I’ve had the 5d4 since Sept 2016. I have no regrets at all. In fact I purchased another one as my second camera as I have drifted into professional photography as a wedding shooter. I am surprised how much I like it and how much my clients love my work.
I tried a Nikon along the way (D800e) and I just did not like the way the photos looked out of camera. They some out with a green cast and skin is magenta looking in comparison. The camera was fine worked great and sharp as hell. I think I am a canon guy, everything just seems a little easier on the canon.
I have zero desire to go to Sony. For me IQ is the main thing. I do not mean measurable specs like DR and that sort of thing I refer to simply how they look and the quality of the files. I personally think even just the raws look great. PPing bulk files is a pleasure.
I am looking forward to Canons alleged foray into Mirrorless pro gear. The one thing I really want is to be able to see exposure in the viewfinder. I am obcessed with manipulating light and that would be a big help. I think it would help me work faster. Silent shooting and IBIS would be cool as well.