I can think of one segment that might go for the FF with GPS - hikers!
I think that those with a good FF camera aren't the target for the 6D. People like me are the target - I own a single DSLR, the 60D , admire 5D2 (and other FF) IQ, would consider getting a second body in FF format, have a mixture of EF-S and EF lenses, with the EF lenses being L lenses that I don't want to "leave behind" in a brand switch to Nikon. Now, would I bother with the 6D? or just get a 5D2, which on IQ seems to be on a par with the 5D3 but lacks some of the features. The 6D and 5D2 seem to be at the same price point, approximately 2,000.00 body only.