I wouldn't be worried about the shortages losing the Wii any sales to be honest. Fact is, it's not even targeting the same market as the 360 and PS3. Nintendo and other companies have successfully targeted casual gamers, but people looking for more hardcore games like MGS4, DMC4, God of War, and others which typically put off the casual gamer due to being too hard, or too complicated will look to the other consoles. Hardcore games don't even tend to do as well on the Wii; Miyamoto himself was disappointed with Twilight Princesses sales on the Wii, and I've heard that Mario Galaxy isn't selling as well as one would expect either, but I can't seem to find sales numbers on that right now (and since I'm visiting family and "borrowing" a neighbours crappy wireless connection, I can't bother to try very hard right now).

The Wii is selling itself successfully as the party system and the system the whole family can pick up and play for 15-30 minutes and have fun doing, without taking the time to master controls, or memorize levels; something the other two have no interest in doing. And at the end of the day, for the casual gamer that is into the stuff the Wii is selling, they're not going to find it on the other systems, so they're not likely to go with the 360 or PS3. Just like the person interested in the more hardcore style games won't find a lot on the Wii that suits them compared to the other two.