Square Enix have said that the Japanese version of Nier for the Xbox 360 will be the international version of the game.
Simply put: Gestalt and Replicant will be released in Japan as two separate games for the 360 and PS3 respectively. But Gestalt will be released on the 360 and PS3 together elsewhere.
At least, that seems to be the assumption according to Andriasang's translation of the latest Famitsu Xbox 360, particuarly an interview with executive producer Yosuke Saito.
Saito also confirms that although there will be no co-op in the game, DLC is being considered.
More through the link.