1. While sales are down, I don't think it's as bad as you're making it sound.
2. Nintendo's software has been surprisingly strong this year. I recommend you pick up Kirby or SMG2.
3. Enough with saying "Wii is a Gamecube on steroids". In terms of raw CPU power, yes. In terms of image and usability for an expanded market, no.
4. I doubt Zelda will be the last hit on Wii. There are more games in development that haven't been announced yet.