There would definitely be some pains going from huge monitors to a small tablet. The bigger side of our plan was that it wouldn't just be possible to develop from a tablet, but really, from anywhere. Develop iPhone apps on your Windows box, or Chromebook, for example.

I think that in the future it might be possible that developing on a tablet might just mean hooking your tablet or other sub $300 device up to two 24+ inch monitors. Think developing iPhone apps from a $25 Raspberry Pi, thanks to the cloud :-)