Don't forget that the uPad itself could actually be much more than we think it is. It is the most capable controller ever made and besides the obvious touchscreen it gives you many other ways to change gameplay in videogames, but still have that controller feel. I feel like the sensor could be really special, it has a lot of potential to enhance gameplay experiences for "core" titles more than a touchscreen or motion controls would.
You can replace ACIII with any other demo. Sony and Microsoft always have a big 3rd party game to show at their Keynote, I just took ACIII, because of their good relationship.
A surprise announcement would be Sim City. I think that it would work amazingly well with the controller.
And don't forget the megatons: Diablo III.
EDIT: Nah, I hope it's this one: