It will be interesting to see how the mainstream audience reacts to the controller. I think a lot of people bought the Wii because it didn't seem intimidating: I remember video after video of old people doing Wii Bowling. The screen on the Wii U seems hip, but I think the iPad is successful in part because there's only really one button (and volume controls/power, of course). Iwata seems to be trying to set investor expectations low for sales. Wii to Wii U isn't going to be the same as iPad to iPad 2.
I think the Wii U will do OK longer term, as Iwata suggests, but the market for it seems narrow. Realistically, how many Wii owners feel they need a half-step upgrade that seems more complicated? How many 360/PS3 owners want another console that's only as good as what they currently have? My view is that the Wii U seems too core for the mainstream, and unnecessary to the core gamer.