So, I’ve made a list of who’s either alive at the end of Infinity War, or who may have made an impact on the ultimate victory despite being dead at the moment, and noted what they can do for us. This is all pulled from other fans’ theories and cast & crew remarks as well as my own observations, of course.
First we’ll address the active fatalities.
Strange: Let’s just get this out of the way, we know Dr. Strange is orchestrating events and that everything he did was for a reason, especially trading the Time Stone to Thanos for Tony’s life. Given the gaps in the opening scene, it seems likely that he used the Time Stone to project himself into the Asgardian ship and recruit Loki, Heimdall, and/or the Hulk. Since this happened in the past, he doesn’t know about it until he does his time travel thing, probably during his jittery meditation scene on Titan. However, he’s a smart guy and he must have realized instantly that Banner landing in his stairwell is no kind of coincidence.
I also expect that he sent himself into the future, so he’ll be the one explaining what’s going on to the survivors of the Snapture.
Loki: Hey, remember when he made a transparent attempt at double-crossing Thanos, cast a significant look at his brother as if to say “I’m still on your side but shh, don’t tell Thanos, who’s looking right at me right now and can see for himself that I’m up to something,” and then whipped out one flimsy little dagger? Wow that’s some masterclass subterfuge, God of Mischief.
In other words, there’s more to it and Loki probably sacrificed himself just to provide a distraction. I think his death is permanent, but that we’ll see him again in a flashback or a message of some kind that explains what he was up to.
Heimdall: His actions could have been the result of contact with Strange, but he’s got his own powers of foresight so it could have been his own initiative as well. Again, I think he really is dead, but that he’ll appear again in some capacity to clear up any doubt that he knew what he was doing using the Bifrost on Hulk rather than saving himself, Thor, Loki, or any number of other Asgardians instead.
Vision: If Shuri has saved his mind (more on that when we get to her), he’ll probably be able to walk us through some vital step toward victory. Why? Because he’s a superintelligent walking computer and there’s never really been an upper limit to his power defined. Even if she hasn’t, we still have his body, and it’s made of the kind of tech that might be really useful for the inventors.
Gamora: The producers have more or less confirmed that she’s within the Soul Stone. Whether this is a state of limbo before she dies permanently, or a way that she might be revived, it still seems more than possible that someone can find a way to communicate with her and that she can tell us something about Thanos, the Infinity Gauntlet/Stones, or the Snapture that helps get everyone else revived.
Yeah, here we were all bracing ourselves against the pain of losing one or more of the original six Avengers, and then ha ha joke’s on us, they’re practically the only ones we get to keep. I don’t know if this has any significance aside from symbolism, but I’m grouping them all together anyway.
Tony: We know that Tony was not only spared by the snap but hand-picked by Strange, who gave up the Time Stone to save his life. Since Strange’s plan clearly involves the snap happening and then being somehow reversed, it’s also possible that it’s not Tony himself who’s important -- this may have just been the best way for Strange to convince Thanos that this wasn’t a trick. However, we also have this very cryptic line from Thanos: “You are not the only one cursed with knowledge.” It’s surprising enough (as Tony himself notices) that Thanos knows who he is, so Tony’s cursed intel is probably relevant. He doesn’t have any particular connection to an Infinity Stone -- what else could draw Thanos’s attention from across the universe? Something Tony knows would have been instrumental for devising a way to stop him. Now it’s going to have to be instrumental in saving the people lost in the snap.
My guess is that Tony learned something during the process of making Ultron and/or Vision. Since Ultron is his biggest regret, he’s buried everything related and mentioned it to nobody. He’ll have to use it to help build something new.
Bruce: Here’s the other key guy. His importance is made instantly clear when Heimdall, the guy who sees everything, Bifrosts the Hulk down to Earth: an odd choice to say the least. Furthermore, he’s sent right to Strange, who takes the wheel from there. Reverting to Bruce Banner, he’s able to report that Thanos is coming and that he has two Infinity Stones already, but he doesn’t seem to know anything about his own role in all this.
Who does know? The Hulk. Something happened on the Asgardian ship which we didn’t see, and it seems that the Hulk received some special instructions that have kept him from making an appearance since then. It could be that the plan needs to be kept secret for it to work, or there might be some specific message he’s carrying until he meets the right person to hear it.
It could also be that the Hulk knows that Banner will be needed and that he won’t be able to return at the crucial moment if Hulk is out. As a science bro, Banner certainly will have something to contribute to whatever Tony, Rocket, and Shuri are working on, and let’s not forget that he also worked on Ultron and Vision.
Natasha: This is a tricky one because she wasn’t used much in the first film, which suggests she’s got more screen time coming, but it also didn’t set her up for much. Aside from just being a general badass or knowing things she shouldn’t have known, I think she might have a moment to shine when she’s the only one who can bring out the Hulk for a chat. She can send him off with a lullaby, after all, so why shouldn’t it work the other way?
Steve: What Steve usually contributes to the team is leadership, and it may be no different this time: the original Avengers remain and will need to get back into form, fast, and work with the very motley crew of other survivors despite their vast differences. Steve’s authoritative voice might help with that.
Of course he’s also got an interesting past that involves the Tesseract and the Red Skull, and in a sense he’s a time traveler. Could the solution be something as wacky as making a new Capsicle and letting him wake up in a distant future from which he can alter events of the past so that none of this ever happened? I don’t know, I got that from a Squirrel Girl comic and it’s getting kind of late while I’m writing this.
Clint: Hell if I know how these movies keep finding a use for a guy whose only talent is shooting arrows with great accuracy, but they do. The master plan might involve a bullseye. He might have another secret, like the one that gave them a safehouse in Age of Ultron. He might just be there for his first class pep talks.
One way or another, though, I wouldn’t be surprised if he shows up in Ant-Man and the Wasp. If so, we ought to get a better idea of what he can do for the team once he catches up to them.
Thor: He’s got the power of the Bifrost, which we’ll almost definitely need for some quick off-planet errands. I wouldn’t put aside Stormbreaker’s other capabilities, either, even though its last hit didn’t quite do the job on Thanos it should have. It might even become important that a piece of Groot is included in the package. Did you think Thor’s whole forging sidequest was low priority? Hell no, the guy knows what he’s about.
Also yeah he’s Thor, he’s super powerful, there will be more fighting and he will be fighting.
Finally, I’m rounding up all the rest of the players still in the game: the cosmic adventurers, the absent but not forgotten, and the Avengers-but-not-originally-Avengers. This of course doesn’t cover every single MCU character who is currently alive (or unconfirmed). If you can think of any others who might make a difference to the plot, I’d love to hear about them.
Rocket: Like Tony, Rocket is a master technician, but put them together and they’re in no way redundant. Rocket’s expertise is in space tech, which is so removed from (MCU standard) advanced Earth tech that it comes off looking like magic. With both combined, who knows where we can get.
A couple other things to note about Rocket: he actually contains some of that space tech, and he’s the last of the Guardians who held the Power Stone. I’m not sure how the latter could come into play, since all the Stones are now in one place and out of reach, but it’s not impossible that “All we need is one person who’s had direct contact with one Infinity Stone!” becomes a thing.
Shuri: Shuri rounds out the trio of technicians and even provides a third area of expertise, considering that Wakandan tech is unique and has particular strengths, applicable to the problem at hand, that the others don’t. More importantly, before abandoning her work on Vision to join the fight, Shuri made some adjustments which may well have downloaded his mind. Whatever she did, she was the last one who worked on him, and the only one who was confident in her chances of separating him from the Mind Stone. It’s pretty likely that we need her.
Scott: The first Ant-Man movie introduced us to the concept of the Quantum Realm, “a reality where all concepts of time and space become irrelevant.” The great thing about this as a storytelling device is that it’s incredibly vague, so they could easily inform us that everything can be fixed if only Scott can go micro and stay sane. Then of course he’s teaming up with the supermechanics, who can devise a way for him to do just that.
Nebula: First thing on Nebula’s agenda, probably, is getting herself and Tony back to Earth. I’m not sure on the status of any of the spacecrafts that got them there, but I feel like this isn’t going to be a major plot point; she just has to give him a fierce pep talk and get him on a ship.
After that, she’s still got a few advantages we might need. Like Gamora, she’s spent her life in the presence of Thanos; like Rocket, she’s got cyborg anatomy. We’ve now canonically seen that her memories can be extracted and played like video, so the question is, what else has she got in there?
Rhodey: I got nothing. The Iron Man movies aren’t my strong suit so I’m not fully clear on what special talents he’s got aside from piloting a second flying suit of armor in case one flying suit of armor isn’t enough. Open to suggestions.
Carol: Okay, if Fury thought she was the best hero to call at a moment like this, I agree, but we haven’t met the character yet and I don’t know much about her history in the comics. She seems to be an Earthborn space denizen (who hasn’t yet bumped into the Guardians I guess?), and I’ve also heard time travel is her jam, so she’s definitely bringing something to the table.
HAHAHA I swear I didn't pick the song playing right now, it was random!