This is what the future of TV should be: people should just think of TV's the way they think of their jamboxes: a higher fidelity dumb pipe for their existing content. If Apple turned the Apple TV into an HDMI dongle that solely included AirPlay and included it for free with every iPad and iPhone they sold, it would truly disrupt TV. If I knew for a fact that every new iDevice owner was necessarily and AppleTV owner, I would immediately start making AppleTV-enabled experiences. Overnight the iPad would become a real competitor to game consoles as well.
It just seems so obvious that this is the right way to go. The apps should live on the brain (your device), and the TV should just be an auxiliary screen, nothing more (We certainly don't need YET ANOTHER SDK for writing TV apps). Here's a fun exercise: go to your local Apple Store and ask them what an Apple TV is for today. Then watch them fumble around mentioning "oh if you have Netflix" and "isn't cable hard to use" and just the sheer lack of vision for the product. If it was just AirPlay it would be as easy to explain as an iPod speaker. If they did this, then you could also imagine indie people shipping TV Shows as apps as a viable model for the first time, completely skirting Cable networks.