Well I went the 1710 route, but I am praying that at least the 170/gen2 can upgrade to the 7900. Imo, it would be a very good sign that Dell cares about the XPS buyers for more than the initial sale, and would spur further sales in the future. That, to me, is what people buy the XPS for, to at least have the option of a better gpu down the road. I'm positive there are enough users out there who would upgrade to justify at least an initial round of cards. It would probably pay, however, to make sure you got in on that round if you wanted one, just to be safe.
Dell has everything to lose and much to gain if they just drop people off the ledge and don't offer future cards for the XPS's. I don't think they "owe" as much to the 9400 crowd, but that's ok, 9400 owners have made their own opportunities
But the XPS folks are going to remember if Dell drops the ball, when it comes time to replace that laptop.
So here's hoping for those that want them, that there is a 7900 and even a G80 option in the future for 170/Gen2 folks.