Eh, no I'm sorry, but I don't buy these rumors one bit. While the low power usage in the Wii U is impressive, as an transitional step between consoles, handhelds, and an eventual unified platform, it doesn't really make sense.
Even a nominal portable device, capable of competing with tablets and smartphones, is going to need a workable battery life, and given where chemistry is right now a portable Wii U would drain any reasonable sized battery very quickly. Sure, with some work you could make improvements to the design that might get it roughly where it needs to be, but, it'd be rather silly to do it like that.
If Nintendo wants an architecture that can give them Wii U or better visuals in a portable, with a workable battery life, it'd be simpler just to use certain architectures and designs AMD's been working on for the past few years.
Not only would it be cheaper for both Nintendo, but it'd result in a less expensive machine that ultimately had greater horsepower.
Now, I do fully accept the idea that Nintendo pushed for low power requirements, and a small form factor, in an attempt to appeal to Japanese consumers. However, I believe this too was somewhat misguided. In terms of form-factor, the PS4 isn't all that much bigger, and Japanese consumers have certainly bought larger consoles in large numbers in the past. Similarly, I do not believe even Japanese consumers pay as much attention to electricity usage as Nintendo seemed to think.