The pictures that were leaked ( http://www.slashgear.com/nintendo-wii-2-stream-leaks-hd-and-... ) suggest that they are abandoning the Wii motion control scheme altogether.
In Crystal Chronicles each player had their own menu, a secret competitive challenge (in an otherwise cooperative game), and a unique view of the area (one gets a map, one gets a dot for every monster, one gets a dot for every chest, one gets information on monster attributes).
Four Swords also used the GBA screen, but it was basically just so you could go in a dungeon and wander off without splitting the screen on the TV or making you stay together.
There were probably more games that used GBAs for private screens or other multiplayer gameplay, but I cannot recall them off the top of my head.
Nintendo is still strongly focussed on making an inclusive family environment, and I can't imagine how each person having a separate screen would help that. Those controllers are almost as big as the Wii itself. You're not going to give that controller to your grandmother as you all sit on the sofa at Christmas. Also, the controller invades on the 3DS's territory a little too much.
It's good news if they do make the most developer-friendly console though, considering their current consoles have the most developer-unfriendly dev process. Hopefully that will extend to their 3rd party developer relations too.
The Wii pointer worked because it had the right shape to be held in a hand and pointed. If this new leaked picture is the actual controller, how are you supposed to hold it in one hand and point? Or are you going to use two hands now?
http://www.cultofmac.com/how-apple-almost-got-microsofts-kin...