The lights are on
For those that are still wondering about how the Wii-U performs against current-gen systems, here's a link:
If you want an idea how it might perform against the PS4:
It would be bad for the Wii-U if the PS4 uses the last processor that was mentioned, but due to costs, I believe that they will not use it, or severely tone it down. Either way, I think Nintendo might be able to at least compete with next-gen consoles.
Also, I know that most of this is based off rumors, but it has been confirmed that the POWER7 architecture will be used for the Wii-U, so even if it is one of the low-end models, it will still clearly out-compete the current generation.