An Engadget tipster sifting through the code for iOS 4.3 beta 3 found mention of "ATVGames" and "ATVThunder," with references to some sort of controller, leaderboards, game scheduling, and a store front. It's hard to imagine that Apple would just flip the switch for iOS 4.3, but it does seem likely that iOS games are gonna show up on your TV at some point down the line.
The image above shows the Incident being played on the big screen, though in this case using the Apple iPad Dock Connector to VGA Adapter. Still! Looks pretty nice.