Canon could do sub-$1000 FF SLRs any time it wants to, and do it profitably. Because it can, does not mean it will, nor mean it should.
That's why I think that any lower priced FF camera will be a surprise entry from a low market share camera company. The big three (Canon, Sony and Nikon) already have FF entries. They're don't want to disturb their margins by introducing a low cost FF camera. They also won't want to cannibalise their higher end models. With the peer pressure on photographers to go full frame, they know that people will happily pay a high price if they feel it will lead to photograhy perfection.
But for Mamiya, Olympus, Panasonic, Samsung, Pentax, Ricoh, Casio etc who are all looking at increasing market shares (and in some cases just want to stay in business), getting into the FF market must look very tempting. And it will be hard for them to compete with the big three. The answer I keep coming back to is to introduce the camera at a low price and make your money on the lenses and on future higher specc'd camera model releases.
Without wanting to be too repetitive, the company I keep coming back to is Pentax. Their K-01 is retailing for $350. What the?? Surely they can just put a FF sensor in their and sell it in the low $1k range? It will have a K mount and would interest a lot of people. My alternative is Samsung, who are very ambitious right now and want to be seen as the world's leading tech company. Surely their camera division are under pressure to gain more profits and market share.