All of the leaked specs and talks have pointed to the Wii U being as powerful as the 360/PS3, maybe a hair more. And honestly if they did make a system that is more powerful than the current ones AND has a touchscreen controller then it would cost $600 for sure which would likely be a huge mistake.
It really wouldn't cost that much for Nintendo to make their console more powerful than both PS3 & 360, especially considering that the tech for that sort is now more cheaper unlike back in 2004-2006.