Brain Age has spawned several imitators, especially in Japan (I read about one just today on GoNintendo about one that asks you to use your non-dominant hand...that's kind of neat, I guess).
So if Wii Sports is a hit (but how can you tell since it comes with every Wii sold (except in Japan)?) then perhaps there will be a variety of other physical games for the Wii. Sports, exercise, aerobics, dance, yoga, Tai Chi, pilates, gymnastics, contortionism, kama sutra...
EDIT: I think I misspelled "kama sutra"...