What would be the point of that and what games would it be able to play with the current, pathetic (gaming-wise) GPU? I think what would suit you more would be the rumored steam box.
It already is with AirPlay and Apple TV. You just need a wireless controller with adequate range to reach your Mac. I'd like to try this sometime as my Mac is actually not far from the television. It's in the room next to it. So if a wireless controller had enough range it should work great.
I would expect the Steam controller will be made to have good range on it to allow for Streaming of games from PCs and Macs to the television, etc.