On December 17, Final Fantasy XIII will be released only on the PS3 in Japan. A million copies have been shipped for launch.
After that initial shipment, another 150,000 copies will be shipped for launch, followed by another 150,000 for the following weekend. A grand total of 1.3 million will be available for purchase during the game's first week in Japan.
By comparison, Square Enix shipped 2 million copies of PlayStation 2 game Final Fantasy XII before the game launched. Of course, the PS3's install base is not quite what the PS2's was.
The Xbox 360 version of FFXIII will not be released in Japan.