I'm placing bets on 2.5's story focusing on either Omega Weapon or Midgardsormr (The latter since they mentioned it quite a few times after defeating Shiva in 2.4's story, surely there's a reason for that).

I'm secretly hoping we're getting another Praetorium-esque dungeon in 2.5 though. They did say they plan to make the 2.x series go out with a bang, after all. Not as big as the Calamity however. A man can dream...