Since how long are we talking to bring computing to TV?
I think that there is a big and if you want a stupid obstacle.
When you want be a passive spectator, you HAVE to be comfortable.
How many times have I come to this conclusion: I prefer my TV than a big cinema screen, because my couch is MUCH MORE comfortable than a movie theatre, and I can watch TV in my pajamas...and also from my bed...
So, if you want to watch TV, you do not want to have a keyboard on your knees or having to be seated to browse.
You do that much better on your desk, with your computer screen in front of you, comfortably seated.
You will never mix the two, especially now, when monitors are so cheap, you can afford to own more than one.
May be you could have your TV connected to the Internet, you could download directly to your TV and THEN sit comfortably in your couch and ENJOY.