The Wii U (rumor says) has a GPU akin to a R770(HD 4830-4870). Last time a rumor mentioned it, it used 40 nm but it's a long time ago and maybe(i wish) they are going to use 32 nm which can fit more flops onto the chip while maintaining heat and power consumption. The first devkits had underclocked hardware because of not finished design and heat problems.
I saw some guy from AMD say the Wii U chip is a 1+ teraflop chip 1.0-1.2 which fits the '4x-5x xbox 360' rumor more or less in terms of flops.
I just don't see Microsoft going all out again when they know casual players are outnumbering 'hardcore' players. They want to push the Kinect 2.0 and what better way to do this than make a console that is cheap while having a proper hardware upgrade. Windows Phone, Windows 7/8 and so on will focus more and more on connectivity with friends and family and Xbox is Microsofts answer to Android TV/Smart TV/Apple TV. It's a media hub for the whole family and releasing a console for $500 in these times is not going to make them succeed.
Also Sony will probably not go and make a 'PS3' again. It didn't sell well in the beginning and it sold at a huge loss.
I think deminishing returns and the finicial situation will force Microsoft and Sony to not make expensive consoles.
