Chris covered everything pretty comprehensively, but just so there's an "official" answer:
1. The dungeon is a weird beast, especially in a game about magic and mind control. It will return, but I need to figure out a reason to justify its existence that won't add another year of work to my plate.
2. Entering dreams was already a thing, as Chris mentions. So yes, it'll return, but don't expect it to work for all 80+ girls in the game ;P
3. Mass of tentacles, definitely not. That would take an insane amount of time to rig and would be functionally impossible to animate. Other forms? Possibly, if I think that a specific dream event would benefit from it, but this isn't a TF game and again, rigging and animation get exponentially harder the more you change the base models.