don't forget, it is common practice to overproduce so that you have extra stock to shove down consumers throats during the holiday season when demand increases 2 to 4 times that non-holiday season. That's the whole reason that this holiday is so insane for wii, they couldn't stockpile at all.
so ask yourself not can wii sell 3.6M a month the entire year but can it sell 43.2M over an entire year? right now,... it probably could.