Future expansions.

The Griffin Empire didn't appear out of nowhere. In "Heroes of Might and Magic V," there's a single-player scenario where, playing as the demons, we eliminate the Falcon dynasty. Consequently, after the Falcon dynasty is destroyed, the Griffins take the leading position.

I think the main focus will be on the Elves. I agree with the reasoning about Railag's fate; he'll probably become a demon and then, after the Cleansing ritual, revert to being an elf.

Humans are unlikely to attack for two reasons:
1) The Faceless Ones are hated by the angels, and reasonable people (including Anton) no longer follow them;
2) Railag asked the Faceless Ones for help, but didn't receive it, so there's not much connecting him to them.
It's more likely that the Dark Elves, led by Railag, will launch an attack.

The reasons for the Academy's appearance have already been stated. Until you provide solid evidence that the previous "clues" mean nothing, I'll remain skeptical. After all, it's not difficult to adjust the plot.