I'm not convinced at all. It looks boring as hell. Plus, it seems it brings nothing the Wii already brought... Those are the same games.
Why would casual gamers want to buy a second Wii, just without the Mario franchise ? They already have their Wii and it's cheaper with more franchises.
Natal will become one of the biggest failures ever.
Casual gamers already got a Wii and it's mostly collecting dust. They won't buy a second one, especially since the 360 is a brand associated with shooters and space marine loving teens. No Mario, no Zelda, no nothing.
Hardcore gamers don't care about waving their arms, they want to play sit, so they won't buy either.