For what its worth: We were at the local country fair yesterday and the local dealer had their usual display of various Mopars. My wife and I were checking out both the Durango and the GC and my wife mentioned she strongly preferred the GC over the Durango, which she felt was "too big" compared to the GC. When I explained its basically the same vehicle, the salesman stepped in to say the 2014 Durango will essentially be a re-badged GC, with even less differentiation that the present models.
I doubt this is true, but there could be a couple of reasons for this happening. First, the GC sells in much greater numbers than the Durango and perhaps Chrysler's research shows that a lot of buyers that cross-shop the two feel the same way my wife does. Or, the Durango is being down-sized slightly so it won't step on the upcoming Wagoneer.
I realize this is all speculation on my part, but maybe someone in the know could shed a little light?
BTW, our trip to the fair resulted in a disagreement over whether she gets a GC next, or I get a Charger RT.