My take:
Controller consists of controller halves flanking a tablet.
Tablet can display same image as tv (at a lower resolution), and touching can be used to navigate menus directly. Alternatively the tablet works like a laptop touchpad as you move the cursor around on the tv.
When playing games, you can detach the tablet part and connect the controller halves together. This allows for better motion control play where motion control is required. Motion control would be more like Sixaxis, and not pointing like Wiimote.
Where motion control is not required, the tablet part can be left on and even be used as a secondary screen if the game supports it. Sorta like FFCC GC with the GBA.
Next, the console can be turned off, but the tablet can still be used as a... tablet like the iPad. Where you can play smaller games you downloaded from an app store, or bonus mini games which are included with certain console games, or even the actual console game itself! The tablet controller functions just like any other regular tablet portable! (w battery and SSD) The controller halves can be left on so you can use physical buttons for games, or removed for touch/motion games.
The console base is a charging cradle, has backwards compatibility ports, and a disk drive for Wii games. Games will be either downloadable or available on discs. Maybe the game plays off the disc and streams where necessary to the controller, or maybe you install the game on a HDD inside the console base. Or maybe the only storage is inside the tablet, and not the base itself.
EDIT: Dual d-pad and stick for when you turn the tablet controller sideways?