Indeed. First quarter 2008. 12 player online confirmed as well. Comes with the little steering wheel thing but you don't need it really.
Don't forget about the other good games on the Wii though.
Metroid Prime 3
Mario Strikers Charged
Battalion Wars 2
Super Paper Mario
Zelda Twilight Princess
If you don't own 3 out of 5 of those games you're really missing out. If you don't own two of those then you should really just smack yourself. If you don't own any then you really have some serious mental issues.
I know I just bought it. SOOOOO AMAZING. Its like Mario 1024 compared to Mario 64. On top of that the graphics are 360 level in my opinion. The music is completely amazing and orchestrated. I've played for a week now fairly avidly and I'm not even halfway done collecting all of the stars. I still have the really hard ones left too.
This goes without saying but if you don't buy Super Mario Galaxy and you own a Wii then you might as well throw your Wii off the roof.