Ok, the 8 GB Next X rumor is partially true. It's a dev kit, as GoogleYourself noted it probably was, and as such they do tend to have about double the RAM of the actual consumer model. It has been confirmed that it was a true "Durango" dev kit being put up for sale (moron).
But we don't know if the 4 GB consumer model will be available for all gaming functions or if a large portion is being held for Kinect 2 and/or the OS.
As for Wii U, we still don't know exactly how much RAM it has.
The rEVOLution is not being televised