I don't think it will.
There's a good chance that the Wii is a fad. (Yes, I have one too.) There's an even better chance that the Wii will look very dated in three years. The best years for the Wii will be these first three. If they sell 12 million a year for three years, that's just 36 million. How many more years after that will people continue to want it as much as they do now?
If people want Wii gameplay, the other consoles only have to release a similar peripheral. It's not a strong barrier to entry. In fact, the PS3 Eye, which does a lot of motion tracking stuff, could take a lot of the novelty away from the Wii.
With price cuts to $99, Wii can prolong its sales when it starts looking like a Xavix game. Then I can see it maybe breaking 50 million.
