Possible, but given their importance in the story I don't see them all suddennly going all zealous and wanting to attack the WoL en masse in the one place and will probably start doing their own thing off in the shadows again, and will continue to be a vague prescence - after all, we're already seeing that with Fannybag declaring "I'm free of the Unsundered's influence, I couldn't care less about restoring the Ancient world, all I want it is to DESTROY EVERYTHING MWHAHAHAHA".

Also we don't know if Pandemonium will bring back Lahabrea, at least completely - a bit of ambigious artwork doesn't mean much (and remembering what Pandemonium was in FFII and IX, it sounds like to me that it will basically be just thematically Palace of the Dead for Ascians - a purgatory where we get to kill bad guys again but really doesn't mean much more for the wider world).

Or I could be completely wrong and it's something completely different no one has considered yet.

We'll see either way soon enough.