I think in a lot of ways that there is a cycle where a "revolutionary" console is successful in one generation, followed by an "evolutionary" console in the following generation. I think in the next generation it will make sense for Nintendo to focus on evolutionary improvement ...
If the Wiimote no longer has to resemble a Remote Control (as much as it currently does) and it doesn't have to double as a NES controller (as much as it currently does) you could probably change the shape a little to make it more comfortable, and change the button layout to make buttons more useable; simply having one or two kidney-shaped buttons on the Wiimote, and reusing the presure sensitive trigger from the Gamecube with the hidden button under it would be an improvement.
The Nunchuck could also include a screen-pointing interface (not necessarily use at the same time as the Wiimote pointing interface), and the analogue stick could use a hidden button under it.
Improving the graphics should be easy, and by the end of 2011 they could (probably) get to a level which is similar to what the PS3/XBox 360 can output at 480p @30fps while the system renders at 1280x1080 (or full 1080p) @60fps, while still selling the console for $300 at a profit (or small loss).
