Two things:
The Cell isn't a standard CPU. Really, there are barely any CPUs that match it's peak computational performance even today. It's peak performance is rated at 230 GFLOPs. The most powerful Core i7 is rated at 65 GFLOPs. As you might imagine, it's just not comparable to normal CPUs. It's a totally different beast.
The other consoles aren't going to be 10x as powerful as Wii U. That's just crazy. There will barely be an Xbox vs. 360 difference between current consoles and the other next-gen systems.
That's false.
You are comparing single precision (Cell) to double precision (the i7), which is 32 bit vs 64 bit.
Desktop processors are almost exclusively rated in double precision, the fastest being the i7 980 @ 109GFLOPS, which is above Cell by 9 GFLOPS.
My AMD 1055t OCed to 3.8GHz is at 75 GFLOPs, which isn't that far away from Cell.
In comparison, an 8 core Power7 is capable of nearly 300 GFLOPS in
double precision, basically blowing Cell to the moon.
Edit: Nevermind. That i7 is not the fastest, it is just the fastest 6-core.