Could be as Steve Ballmer, big cheese of Microsoft, stated in an interview
that they may have more form factors and price options in the future. Microsoft has never done a redesign of a console but they haven't been in the industry as long as the other veterans in this area. Sony's one that always comes out with a new design for their PlayStation line and Nintendo has variants of their handhelds.
I would definitely like to see a slimmer version of the 360 though as well as a smaller footprint. I do wish they would use a slot loading DVD drive rather than the tray as both the PlayStation 3 and the Wii use slot loaders that, to me, offer one less part to break. I can't tell you how many times I'm in the midst of changing a game on my 360 with the tray out only to have my dog or my son come wandering close by at high speeds.
So, if there are different form factors in the works, what do you want to see?