The Fall 2011 XBox Dashboard update is coming, and it's looking like it is going to be a huge UI overhaul.
Probably the most dramatic change is the implementation of a very Windows-Mobile-7-looking Metro interface. I find this very interesting because at a point in the future Windows Mobile, XBox, and Windows will have a very similar look and feel, which is not the case today. Engadget's Sean Buckley describes the new look as very "tablet-esque," and while categories take up less space on the screen, the changes seem "more refined than cramped."
Kinect integration continues to be improved, with many more Xbox functions Kinect-controllable. Voice control will be possible in more places, and voice search via Bing integration may provide some interesting functionality, such as searching for "Batman" and getting back a list of ways to watch Batman on your Xbox. Friend management will change as well, with the ability to push status messages and achievements out to Facebook.