I'd say you're almost correct. Here's one possible theory: Nintendo doesn`t have to release many more games for this generation.
How many Zeldas did the gamecube get? Mario Karts? Smash Brothers?
Now just look at the charts, there's pretty much 3-5 Wii games, published by Nintendo that are consistently in the top 10 (Wii Play, MKWii, WiiFit, SSBWii, and maybe one or two I'm forgetting). If sales continue to remain consistent then why would they need to release any more games?
As seen with Wii Music, not everything Nintendo does is solid gold, so why introduce more potentially less lucrative titles that'll just cannabilize the stuff that's already making truckloads of cash?