Currently, there’s a quip from Gamepro’s interview with Nintendo’s Shigeru Miyamoto floating around that claims the Wii-U can only support one tablet at a time. This claim would explain the multiplayer games found in Nintendo’s booth, all of which allowed only a single player to use the tablet. In Battle Mii, two Wiimote+Nunchuck wielding players fought one tablet using player. In Catch Mii, four players used the Wiimote to chase a single tablet user.
Hopefully this is being taken out of context, with Miyamoto meaning that only the current prototypes can allow one tablet. There are a couple of reasons to think this may not change, however. For one, the controller will likely be expensive; bundling it with the console will help take out some of the sting, but no one will be racing to buy multiple controllers that will certainly be priced higher than the current standard of $50. Second, the system has to stream a video signal to the tablet, and the quality of the video isn’t much of a slouch. Most likely, the Wii-U, while certainly powerful, likely couldn’t handle running multiple video streams simultaneously with the HD signal from the console. Add that on top of all the graphics and command (plus motion) processing that has to be done, and you’re looking at a decent amount of data to process.
Here’s hoping there’s a simple miscommunication, but there is definitely a chance that this will become the standard in holiday 2012.