Dream Drop Distance Jump Festa Trailer

I'm putting this in Spoiler's because I'm not sure who here might not have seen the trailer

Spoiler

So how come Vanitas was in this trailer? At the end they end up showing a Young Master Xehanort and Vanitas saying to Sora that there are more hearts in him, but why would he be there? Is it because Sora has Ven's heart inside of him, and because Vantias is a part of Ven he's also inside Sora? But since he was destroyed by Ven, why would he appear? Anyone have they're own theories on this?

 

Dreams of things that have happened. I think that's probably the point.

Both Sora and Ven may be experiencing shared dreams of what has happened to them in the past, and what they both share to a high degree is fighting their ultimate counterparts, which for Sora is Xehanort and Ven is Vanitas.

And the center of this game is the them of dreaming, so those two could just be images or illusions created by someone or something else, like Yen Sid.