I wouldn't be shocked if we saw a $1000-$1500 FF mirorrless camera within the next two years. I see the 6D and 600D as game changers. Suddenly, we have reasonably specc'd FF cameras being released with $2k price tags.
For typical camera users, I see the current bread and butter models as follows:
M4/3 - Olympus EPL5 - $599
APS-C - Sony Nex 5R - $648
APS-C - Canon T4i - $799
FF - Canon 6D - $2,000
FF - Nikon D600 - $2,000
I know my logic can be countered in a number of ways, but if I was a camera company exec, I'd be thinking that there's a big hole between $800 and $2000. What would get the camera community excited? A cheap FF camera. I'd then work backwards, basing everything upon a final sale price of $1250 - $1500. Ultimately, I end up with a very simple mirrorless camera with an EVF and a FF sensor. I end up with a Nex 5, but with a FF sensor and a $600-$800 premium. (And going by most of the comments above, an $800 price increase isn't unreaslistic to cover the price of a full frame sensor).
Over its lifespan, this camera will decrease in value. Come end of life, you will see run out specials below $1,000. Maybe in 4 years time.
The big question is, will it be a Canon? Sadly, I think not. As a betting person, I'm liking the odds on Pentax who have a lot of legacy FF lenses and users to satisfy.