A drought late next year is certainly possible, complete Wii failure is possible too...if you consider it a real concern, then don't buy the system until some more games are announced.
If I had the willpower to wait, I'd buy a Wii after the first price drop. By then I'll have a much better idea of how good software support for the system is, plus I could save some money. But the system looks like too much fun to wait for, and there are easily enough good games at launch to justify a purchase.
All that being said, EA and Ubisoft have already proven to be quite dedicated to Wii, and word from Nintendo is that third party interest is higher than GameCube so far. I think 2007 is going to be a fine year for Wii.