Off topic - Japan is the least affected by the economic crisis. The Yen hardly dropped and there has been no panic what so ever from the Japanese people regarding money issues or economical crisis in Japan. They are still spending big on their brands here.
On topic - I dont see Fable 2 or Banjo being system sellers in Japan. They may increase software sales but wont move much hardware. The next big spike for the 360 is Last Remnant bundle in Japan next month. Fable 2 being a WRPG wont move much at all in Japan and its release is 2nd last week of december so i dont see it moving hardware to those numbers you predicted.