If Apple were ever to release even just a standard Bluetooth game controller that worked with iPad + Apple TV + iMacs ... that could be a game changer.
I suspect in the next few years Apple is going to push the iPad being able to wirelessly interface with televisions too.
So if you have an iPad, just get in range of your TV, pick up your controller and you can play, no cables (ala the Wii U concept only the hardware is in the tablet itself).