Twice as powerful wouldn't be that much, if MicroSony take the same route they took this gen, and make the consoles very powerful, they'll easily make the Wii U look dated, Wii U will be behind in Graphics, Physics, AI, and probably online player counts. This wouldn't help them with third party support, which they are apparently trying to win back, because games will easily look and run better on other consoles, leading to better sales on other consoles.
But I guess Wii never needed powerful next-gen hardware to succeed, so I doubt the Wii U will either.
These are just rumours though so I really don't know what will actually happen.