Its doubtful they would be able to get enough processing power for 4 screens in there, but who knows, if they do it will be sweet.
//Idea, make it so that your WiiU controller is more like a gameboy, but it has to be at Some WiiU console machine to do the heavy processor lifting. Put some flash memory in the WiiU controller, so you can store virtual games and saves, and take them with you to your friends house for multiplayer games. A Lan party in a box..