I'm starting to get the strategy, the
wiiU is fully compatible with the wii, so it's a disguise
Wii Upgrade, if you own a wii, no cost added as you are likely to have multiple wiimote and balancee board and start directly from here to new game.
I guess the only one tablet per console si also to avoid proliferation of controller (wiimote, nunchuk, classic, balance, tablet) and also to secure first generation of game that actually use the tablet in new non obvious way and ease the adoption without forcing people to invest too soon.
Also the tablet is also a new standardization as camera, mic and touch does not require new separate hardware, that mean that game can use those feature as standard. Still they need to find a way to integrate all of this in only one controller (no idea how, but nintendo is their name).
Also if online goes well, we might have vid chat as a standard for almost every game.
They seriously need upscaling

too as smash and many game look hd worthy (sonic color) and hope they have extra gimmick if we put skyward sword on that. I also hope that the streaming work for every wii game too.