There is an actual processor listed in the patent, so the Mouse would have some capability of its own to run integrated apps. You may be able to set up parts of the touch display surface to work as buttons, maybe to handle special functions in games or apps. And the patent also says that this display technology could be used in the Magic Trackpad or even in the MacBook trackpad itself, providing an extra space for displaying graphics wherever the user has a touch interface to play with.
It's an interesting idea. As with most of these patents, it sounds like this is simply something Apple is researching rather than actual technology going into an approaching Magic Mouse refresh -- there are a lot of elements that have to be worked out (like why would you put a display on a device usually covered by your hand?) before this kind of thing goes on sale. But it is an interesting idea, and we may one day see Apple use it in a real product.