I think it's just Japanese gamers realizing that even though FFXIII is still exclusive to PS3 in Japan, 360 is a viable RPG console to get FF moved to in the rest of the world. This is just a theory but FFXIII announcement was most likely huge among Japanese core gamers and perhaps that announcement made them rethink their view on the console.
In the end, I have no clue. Good for 360 though. Maybe, it will finally break a million.
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PC, XBox 360, Wii, PS2, DS, PS3