Anyway, I did have a random moment of speculation that I thought I might share for now. We've been told that there are three options for what will happen to the Seed: it stays where it is and the world continues on, it's removed and all the demons pop out and eat us, or it's broken and the world loses its entire connection to magic. Since it was shown as broken in Buffy's glimpse to the future in which she's betrayed, I haven't really considered the other two possibilities very deeply.
But here's the weird thing about the Seed: it's shaped like an egg. Not a lot of things look like eggs, except for eggs. What happens to eggs if they don't get broken?
If that thing stays on its pedestal (and indeed, that vision did appear to leave it there, and it wasn't so much smashed as cracked open), what could hatch out of it?