With an already bottlenecked CPU, er no.

Okay fine let me ask again, is the NX a seperate processing unit CPU/GPU for the Wii U?

Who really knows, everyone has their own idea's. We will find out for sure next year.

Well, we can forget about the handled device theory because of this very clear patent claim:

5.) The gaming system as recited in claim 1, wherein the supplemental computing device does not include a display driver, an audio driver, and a user-control interface.

Its just a patent, if you went of on what sony is doing based on patents you'd be gaming with a screen in your brain and a control unit up your arse.

No that wouldn't be possible with the Wii U because it's external ports are far too slow (USB 2.0) to handle a "supplemental CPU/GPU" ... this is likely for NX, and NX is likely not one single product but a family of products. 

The "supplemental computing device" wouldn't need a display output though as the primary (handheld) would have one already though. 

It would likely just be a box with a high CPU + GPU + maybe a HDD and then a high speed data output  to the primary device (ie: NX Main Console or NX Portable). 

Is USB 2.0 too slow to carry HD audio and Video?

Quick question though (and maybe it is something I missed) by why are you certain that there is a portable involved?

Well it is labelled as "supplemental" meaning it probably still uses some of the hardware from the primary hardware device (Base Console or HH). 

IE: It's possible for example that the "Supplemental NX" doesn't have any audio processing of any kind and all that is done by the primary device. This would require the two devices to be able to interface with each to sync everything properly very quickly. Don't think USB 2.0 can handle that. 

I'd guess in this setup the Base NX would run all OS features and that sort of thing too.