Just as many rumours that PS4 will be CELL based than the ones that it will not. So hardly a basis for factual discussion.
As for Wii U, the only official release of CPU spec from Nintendo is as follows:
IBM Power Architecture-based multi-core 45 nm microprocessor based on the POWER7 architecture found in the Watson supercomputer.
The rest is pure speculation.
Regarding "the desktop" as a yardstick, it's worth noting that more "computing" is now being performed on mobile devices than anything else. The classic PC model is dying, smartphones, pads and consoles are becoming the norm. Even a lot of PC owners use mobile devices and consoles more hours per day than their PC's. I for one count more Wii hours than any other computational device I own, and I own a lot of them (as do many others on this forum).