Definitely PS3 exclusive. One reason cuz of the size of the game. Kojima said that it filled an entire blu-ray disc. Assuming that it is a double layer 50gb disc he used I just dont see a game in the future being released for 360 taking up 6+ double layer dvd's just for the game. Its just too big for the 360 to handle. And swapping discs for installation would b a pain. Also it would isolate many 360 players from playing the game if they own the 360 model with no HDD. So its definitely staying on the PS3.