There’s the Android emulator out there (I don’t recall what it’s called), plus there’s VMware-like solutions, with Android VM images. I sort of wonder if there’s anything like that you could run on top of the Ubuntu-on-Nexus to get a tablet that is fully usable with both Ubuntu and Android simultaneously.

And, then, there’s the future possibility of the lesser option: someone creates a way to dual boot between Ubuntu and Android.

The thing I sort of hope for:
a) ChromeOS as the base layer, with all of the things it does to handle integrity of the underlying OS
b) the ability to run Ubuntu and/or Android in virtual environments on top of ChromeOS

Then you’ve got a good solid, lean fast booting infrastructure, but the flexibility and power to still do real work (Ubuntu) or recreational tablet stuff (Android).