According to VGC MS just sold through their shipped consoles from last year.

[DirtyP2002]

Hey,

I just noticed that the current sold Xbox 360s on VGC is the exact number MS reported to have shipped end of last year. This means back then MS had enough consoles in stores for more than a quarter or 112 days or 30.7 % of the year.

According to VGC they have shipped enough consoles for the next 110 days already.

But there is always the "wait for next quarter" logic.