You DO NOT want to run a desktop user interface on a tablet.
Was Unity specifically designed for a tablet? Does the window system have multitouch support? Accelerometer support? Do any of the applications themselves support multitouch and accelerometers?
I'm not saying that the same desktop OS will run on both devices, but rather that the overall UI and functionality can be shared.
Though, in a couple of years, who's to say that Ubuntu won't be able to run on most devices? Maybe there are challanges, but I doubt that it would be impossible. It's just a matter of time and maturity.
I think people are already asking for one user environment across devices, so I bet it's something they might have in mind.
Was Unity specifically designed for a tablet? Does the window system have multitouch support? Accelerometer support? Do any of the applications themselves support multitouch and accelerometers?