This is educated guess rumors for the Wii U Specs and they seem to be legit type observations.

CPU: POWER7 Processor
“Nintendo isn’t screwing around when it comes to their CPU in the Wii U!”

Quad Core Processor
4 Fully Functioning Independent Cores
Unified Shader Architecture
Xbox 360 has 3 Cores
PS3 has 7 Non Physical Cores – One is disabled and another is used for the PS3 OS – 5 Cores Total

Clock Rate: 2.4 – 4.25 Ghz (I’m going to say 3.0 Ghz processor (rounder number) even though I would want Nintendo to max out at 4.25 Ghz and keep in mind these are low end numbers for the Power7 Processors there are Higher Speeds and Specs!)
L1 Cache: 64KB Per Core (32KB Data + 32KB Instructions) – 256 KB Total (128KB Data Total + 128KB Instructions Total)
L2 Cache: 256 KB Per Core ( 1024MB Total)
L3 Cache: 4MB – 8MB Per Core (16MB – 32MB Total)

4 Threads of Code at Once per Core (16 Threads of Code at Once Total)
Intel Quad Core I7 has 8 Threads of Code at Once
Xbox360 6 Threads of Code at Once
PS3 6 Tasks at Once
PS3 hard to develop for as they are not individual cores and rely on PowerPC for instructions.

“If Wii U uses an Entry Level Power7 Quad Core Processor it’s Capabilities Destroy the Cell Processor, Hands Down!”

Video / GPU: AMD/ATI Radeon HD 4850 (Wii U GPU – AMD Radeon R700 Series)
Using ATI Radeon HD 4700 Specs (slightly less equivilant but similar) to HD 4850
Core Speed: 750 Mhz
Shader Clock: 750 Mhz
Memory Speed 1600 Mhz GDDR5
Memory Bandwidth: 51.2 GB / Spec
Pixel Fill Rate: 12000 MPixels/sec
Texture Fill Rate: 24000 MTexels/sec

50% More Powerful than Xbox 360 – Double Preformance of Xbox 360
“Wii U Wipes the Floor with the PS3 Graphics Chip”

Bottom Line: “It is almost impossible for Nintendo to make the Wii U less powerful than Current Generation Consoles. If Nintendo asked Nvidia to use the 8800GT (which is a 5 year old GPU) it will still blow away the graphics processors in the xbox 360 and ps3 and it is 5 years old!!!!, and cost next to nothing now!!!”

[Source]