Most people I know who played video games regularly on the PS2/Gamecube bought a Wii at launch and traded it off for a PS3 or 360 around two years ago. I say PS2/Gamecube because the people who had an Xbox last gen got the 360 within a year for Halo or whatever.
I don't really mind what is happening to the Wii. Thinking back, I bought it to play Nintendo games. I still want to check out Red Steel 2, Fragile and a few other third party games but mostly I'm content with it being my Nintendo game box. Mario Galaxy 2, Sin and Punishment 2 and Metroid Other M all within the next four months. That's pretty great.
Things like Wii Fit, Just Dance, w/e aren't for me. They're cheap games for people who bought the Wii as a novelty and they're happy with it. The Wii is the Telemundo of video games and who am I to say that audience shouldn't enjoy 12 Corazones?