The latest generation of microprojectors would make more sense than really big displays. Imagine buying something roughly the size of an AppleTV or Mac Mini which also is the television - you just point it at a white wall or sheet or screen for a nearly arbitrarily-sized screen.

I use a projector tv at home now but it's a pain to configure because it's designed to work with too many kinds of input. Integrate a more compact and elegantly designed projector with iTV, make iPad and iPhone your control surfaces but download content from the cloud - it could work. And unlike the big flatscreen, it'd be easy to take to the Apple Store for service/diagnostic if need be.