In the business sense I totally agree with you actually I agree with pretty much everything you said, But for the hobbyist it will have to be significant or maybe it won’t, most people on this page would probably buy one just to say they did and make a YouTube video about it. For those who don’t shoot professionally to say the camera needs a tilty flippy screen or some other dumb feature that would detract from reliability don’t understand canon or the pro user. I don’t want anything that could potentially break or render my camera body useless. Would illuminated buttons be nice? Maybe but I have memorized where the buttons are, we working professionals don’t need the gimmick, we want proven reliability. I shoot in mud and down pouring rain at times and a evf seems like a point of failure for those situations.'People' perhaps, but it'll be simple for commercial outfits who will have depreciated their 1DX2s. When you're relying on depreciation to reduce income tax libaility then it makes sense to switch-up and restart the cycle.
Personally I think the 1DX3 will have a resolution bump, dual CFast and perhaps an AF push to all-cross-points, but little else. Certainly no swivel screens or illuminated buttons that aren't compatible with 3 - 5 years of hard daily use.