Well, I don't believe that PS3 rumor thats for one thing. Second thing...I do believe Square Enix might announce something regarding KH: BBS and KH: 358/7 Days, other than that. KH3 is going to be under wraps until those PSP/DS games are on playable form and are ready for shipment.
To add my two cents, I would like to see KH3 on the following and why:
PS3: It would be nice to have KH3 on the PS3, since KH and KH2 was on the PS2, and Trophies, DLC
Xbox 360: Achievements, DLC
Wii: Use of the Wii-mote