i think it will be a PS3 exclusive cause if they wanted to put it on the Wii then they would have announced it by now of the previous DS KH game.
they wouldn't release a trailer on the PSP saying its coming on the PS3 and Wii.
Also they could have been waiting for the FF13 launch sales to put the trailer for the next game in the PSP as a PS3 exclusive or as multi-plat.So if FF13 sales were good then they would keep it as PS3 exclusive