So basically Canon will tell it's crop users that want to move to FF to look at other brands (like the D750)
How so? Are you already assuming that a future 6DII will be uncompetitive when it debuts?
Also, I know many users of APS-C bodies that own one or more EF lenses (myself included) which provides a good incentive to remain with Canon.
It is a always a trade of. In my case I am looking at FF for improved IQ. Currently the 6D is the best balance of price/IQ. If the price of 6DII goes to the neighborhood of 5DIII then that is no longer a case. From what I have read the D750 has a better IQ then the 6D, currently 6D wins on price but looses on AF.
The few FF lenses that I have are more applicable to the 1.6 crop factor and they would not be so desirable on FF, this is why replacing them by changing brand would not be a big sacrifice.
The other part of my problem with Canon, and that has nothing to do with future price of 6D is why the control layout between different levels of cameras is so different. Somebody who starts with a xxxD and moves to xxD or xD will have to relearn muscle memory for controlling the camera. If you have to relearn all the layout then what is keeping you with a brand. I don't know if that is the same with other manufactures, but I think that is so stupid.
The 7DII is virtually identical to the 5DIII and that makes a lot of sense.