Why is everyone assuming that the Wii U will be the weakest of the next gen consoles? We don't know if Sony will have a Wii-esque console of their own next generation, nor do we know much of anything about Durango, and the idea that the Wii U has to be a half-step seems to stem simply from the existence of the Wii and ignores the gamecube, N64, and SNES before it. If Nintendo wants to have a console that's as powerful as they can feasibly make, then they will. This idea that Nintendo literally can't compete in that manner is silly. The only credibility this idea has is in the fact that Wii U will presumably be launching first, giving MS and Sony a few months to wait for cheaper/stronger components. Outside of that, we really don't know.
My money is that all consoles will be of more or less equal parity, similar to PS2/GC/XB, and we'll really never see one console that clearly outperforms the other. As I've said before, the additional features of the console, their online functionality, and their method of control will become much more important factors.