I've heard the theory many times that Sora will eventually turn to darkness, hell maybe even become the MoM. Well, if the MoM is actually evil like we think, here's my thoughts. Sora is holding Xehanort's Chess Piece, he's currently with the dark side of Xehanort. This is my theory, but what if Sora, similarly to Aqua, falls to darkness? He's trapped in that area for so long with nobody around, and has no way out. Eventually, he's trapped and falls to darkness. This would also line up that Sora is holding Xehanort's Chess Piece all alone, seemingly after the events of the final boss.

It sounds fucking crazy, but then again...we're talking about KH here.