Lahabrea went through the dragon's eye, and is currently terrorizing Pelamar. If this is not canon, I'm making it canon.
As for the other Ascians. I doubt we'll see them for a while... The last... Three? To come at us have all ended up dead, despite their belief that death is off the table for them. Add to that the group we Akh Morn'd and yeah, I don't think they're going to want to stand toe to toe with us for a while... We are clearly dangerous, I think they're going to go back to working in the shadows rather than getting directly involved. Props to any of them that still have the balls to go up against us directly, but it was already stupid enough having the Twelfth Chalice go "Did you think this was over when you killed Lahabrea?!" to "How could you possibly defeat me after I acknowledged that you bested Lahabrea?! Oh... Right... I'm an idiot...", I really hope that kind of crap doesn't happen in the Main Scenario... It's fine for the bumbling Saturday morning cartoon villains that Job quests seem to draw, but if Altima comes rocking about in 3.2, all overconfident in her supposed immortality, only to act shocked when we kill her, I'm going to be somewhat peeved... They should be much less aggressive in their tactics now that we can clearly kill them...
Lahabrea is the only one I want to see make a comeback, because he clearly had some other goal in mind... He seemed to consider himself above his peers, granted they all do, but Nabrialis was speeding on the next Rejoining so he could be Zodiarks right hand, he still considered Zodiark greater than himself... Lahabrea gave a few subtle hints that he considered himself above even Zodiark. I mean, his area of interest was gifting people the ability to summon Primals unto themselves, I can totally see his endgame being to become Zodiark, rather than to revive him, which is the goal of the rest of the Ascians. Plus, if he has become Nidhoggs eye floater, we have the perfect chance to bring Shinryu into the game; Lahabrea compels Nidhogg to fight fire with fire. Thordan VII summoned a Primal unto himself, so lets have Nidhogg summon one too. The Primal Shinryu comes into being through Nidhogg, Omega reactivates to fulfill its tradition of hunting down Shinryu (Allag made it to best Bahamut here of course, but Shinryu and Bahamut would both be Celestial Dragon Primals, not a lot of differences when you think about it), in the chaos Lahabrea slips away to prepare our 3.5 encounter with Zodiark. We beat Lahadiark, rest of the Ascians finally give up, 4.0 can be something refreshing.