Given how little we know about the NGP and how recently it's been announced, I would be very surprised to hear that Square Enix would be releasing BBS2 on it. Production on Versus XIII seems to be winding down, so I imagine an official announcement of production on Kingdom Hearts III is not too far away. I expect then that they'll want to be pushing BBS2 out as quickly as they can, and that would mean releasing it on the PSP instead of waiting for the NGP.