Well, I have the 1DX and I have ordered a 7DII. There are three reasons for this.
The first is to use the 7DII with the long whites for reach limited cases. Yes, I know that a cropped 1DX image, from a pure IQ perspective, in many cases will be just as good, especially higher ISO. But I mostly shoot lower ISO, where the IQ difference is minor and I expect the AF system on the 7DII to improve my focus on long reach. It will also give me more pixels for larger prints. I also had the 7D MkI, which I never used for this purpose, due to its inferior AF system and IQ.
The secondary reason is size and weight. When I go for long hikes in the mountains, looking for birds and wildlife, a 7DII/200-400 f4L IS 1.4x combo will cover all of my needs. And it is both lighter, smaller and more flexible than carrying the 1DX and the 600 f4L IS II, with extenders.
The third reason is for my wife to use with a Tamron 16-300 super zoom, when we travel. She does not like to change lenses ...