It would be kinda corny, but I see some possibility in this. We know Vanitas looks a whole lot like Sora, right? Well I thought how at the secret ending of BBS it hints on Sora saving people connected to him. Maybe Vanitas will return and pose as Sora and do evil stuff during his adventure.
If you haven't seen Vanitas face then here you go:
No flaming!
If you haven't seen Vanitas face then here you go:
No flaming!