Let's get some stats in here.
Last year (2009), the sales were as following:
Wii: 344K
Ps3: 161K
X360: 178K
If we now look at start of Nov-19Dec in both 2008 and 2009, the difference is
2008:
Wii - 7.3 million
Ps3 - 2.4 million
X360 - 3.85 million
2009:
Wii - 7 million
Ps3 - 4 million
X360 - 3 million
Going by that, we would be looking at 300-350K/week for Wii, 250-275K for Ps3 and 140-165K/week for the X360.
However, I think the differences will be somewhat lower than that. The Wii and Ps3 should be a bit lower, as the price cut effect wears off a bit, at least.
All in all, I wouldn't say that the OP's predictions are too unlikely.