As you can see in my signature, these are the rough numbers I expect for end of 07...
Wii - 18,000,000
Xbox 360 - 14,000,000
PS3 - 6,500,000
Nintendo will not be stupid enough to let this holday seasons go by. They will have their shipping/production issues solved by then. Wii is (still) the hot item to get, and Nintendo could steal ALL the thunder from it's competitors with a bit of a price cut. 18m at the very least. And don't forget Super Mario Galaxy... remember that Gamecube had over 200% increas on Sunshine's release.