Well, I'm not sure what MS has learned from the Wii but I've learned that a new gimmick can sell a lot of consoles for a reasonable time but it can't help selling a lot games because the hardware was too weak to satisfy the expectations of users and devs.
And seemingly the users also learned a lesson from not really buying into Nintendo's next gimmick again because the old one collected dust.
Attach rates on all 3 7th generation consoles are actually quite comparable.
Only Microsoft's box had an advantage by approximately 1 game per system. The "buy for Wii sports and let it collect dust and buy no games it's a fad" thing is disputed by facts.
That the Wii U's not setting the entire world on fire is a separate discussion, but you should know that Kinect is a very important tool to Microsoft.