The AppleTV is already iOS behind the scenes (and uses the same A4 chipset as the current iPhone and iPod touch). Technically, it'd be possible to run iOS games on the Apple TV nearly unmodified, and use your other iOS devices as controllers. Also, the iPad 2 will be able to do full video mirroring over the network to the Apple TV as of iOS 5; presuming the performance is up to spec it'd be possible to "invade" living room gaming that way as well.