So after watching the most recent trailer, I was left both even more excited and confused than before. One thing, however, caught me eye. At the beginning, middle, and end of the trailer, it shows Terra Ven and Aqua in places that look like/are Castle Oblivion.
Terra running through a corridor that appears to be the same as the ones in Castle Oblivion
Ven it what appears to be the Champer of Repose/Room of Waking. No solid evidence yet.
Aqua standing outside of the door to Castle Oblivion.
Now, BFMV95 had a theory that said:
If this theory is true, then a lot of things involving Castle Oblivion would make a lot of sense.
I feel that Ven may very well have somehow connected his heart to Sora's, and for whatever reason, his body is being held in Castle Oblivion. In 358, Saix and Axel have a bunch of conversations and one of them was about Axel searching for a room that he couldn't find. When Roxas and Axel go to Castle Oblivion, Roxas has a mini freakout and is unable to go on. This could be his body reacting to Vens presence somewhere in the castle. Since Aqua's armor and Keyblade are seen in Castle Oblivion in KHII:FM+ its likely that all three of the characters stories come to an end there...

Terra running through a corridor that appears to be the same as the ones in Castle Oblivion

Ven it what appears to be the Champer of Repose/Room of Waking. No solid evidence yet.

Aqua standing outside of the door to Castle Oblivion.
Now, BFMV95 had a theory that said:
Well, I was watching the new trailer for BBS and I noticed that Ansem the Wise talks about "that boy" who saves the world each time when the darkness shows up. He also mentions that he can connect with other peoples hearts. Ven says "Our connected hearts are my power!" which means that "that boy" is Ven, at the end of the trailer, Ansem the Wise says "And his name is..." and it shows a picture of Sora.
So I think Sora's heart is connected to Ven's heart, so when Sora became a heartless and Roxas was born, he had the apperance of Ven due to the fact that Sora and Ven have connected hearts.
Think about it, it all makes sense.
If this theory is true, then a lot of things involving Castle Oblivion would make a lot of sense.
I feel that Ven may very well have somehow connected his heart to Sora's, and for whatever reason, his body is being held in Castle Oblivion. In 358, Saix and Axel have a bunch of conversations and one of them was about Axel searching for a room that he couldn't find. When Roxas and Axel go to Castle Oblivion, Roxas has a mini freakout and is unable to go on. This could be his body reacting to Vens presence somewhere in the castle. Since Aqua's armor and Keyblade are seen in Castle Oblivion in KHII:FM+ its likely that all three of the characters stories come to an end there...