I have a theory that Zexion is still alive and well. It's quite far-fetched, but we don't have enough information to prove it wrong or true:
In this picture we see someone with sort of long, silver hair carrying one of the knights up the mountain towards Kingdom Hearts (or just gazing at it).
In the PV we also see an Unknown figure, clearly from Organization XIII, walk into the room in the basement of Hollow Bastion and sit down with an armor-wearing knight in a pile on the floor. This could be Zexion, who comes to collect the knight and for some reason takes him to Kingdom Hearts, as we see in the above picture.
It's a far out theory, but I think it could be possible. We all know that Zexion never really died (of course, he could just be dead, and Nomura is teasing us with all of this random information about him).
If you have anything to back this theory up or shut it down, I'd be glad to hear it. Any thoughts, as well, because I think this could be true.

In this picture we see someone with sort of long, silver hair carrying one of the knights up the mountain towards Kingdom Hearts (or just gazing at it).
In the PV we also see an Unknown figure, clearly from Organization XIII, walk into the room in the basement of Hollow Bastion and sit down with an armor-wearing knight in a pile on the floor. This could be Zexion, who comes to collect the knight and for some reason takes him to Kingdom Hearts, as we see in the above picture.
It's a far out theory, but I think it could be possible. We all know that Zexion never really died (of course, he could just be dead, and Nomura is teasing us with all of this random information about him).
If you have anything to back this theory up or shut it down, I'd be glad to hear it. Any thoughts, as well, because I think this could be true.