Nintendo simply does not have the stock to fulfill demand. MASSES of people are going to go home pissed off this Christmas. We all know that Christmas is the time where everyone buys big gifts.
So do you really think that people will be after Wiis next XMAS, or would they have just given up? I find it very possible that Wii will be old news by next Christmas. No one is going to buy a piece of paper for XMAS guaranteeing a Wii in the future. No one wants a present-less XMAS.
Next year, people could very well remember the Wii as the gift they could never find.