Updated with more info.
Its stacking up to be a very much equal three way race in tech power. Personally, I think Wii U is making the smarter choices.
CPUs are looking to be neXtBox>Wii U>PS4.
GPUs are looking to be nextBox>=PS4>Wii U
GPU race is a little more complicated tho. It really is going to depend on the tweaks each manufacture has done to the base chip. Off the shelf, I'd argue Wii U's GPU is greater than PS4s, but I know Sony will be adjusting that greatly, so in the end they will be slightly better considering its going with a design a few years newer.
All in all... the three will easily beat down current gen and will be remarkably similar in capabilities to each other.