Wii Fit and Wii Music are old IP. Namely, uh, the Wii brand. It's been around for about a year, maybe you've heard of it. Just because they have different gameplay doesn't necesarily make them new IP, unless Mario Party is a seperate IP.
But, as Bod pointed out, Nintendo are having huge success with new IP right now. And though Wii Fit isn't technically new IP, I think everyone will agree it is shaping up to be another revolutionary game like Brain Age, Nintendogs and Wii Sports.
Simply applying some new IP instead of old IP to revolutionary gameplay doesn't make it more revolutionary. You can't downgrade Nintendo because they've pushed great new concepts within existing brands like Mario, Wario, Zelda, Wii, etc.
Hopefully Nintendo will still have some new IP next year, though.
"[Our former customers] are unable to find software which they WANT to play."
"The way to solve this problem lies in how to communicate what kind of games [they CAN play]."
Satoru Iwata, Nintendo President. Only slightly paraphrased.
