I respect your opinion, though I disagree. Many/most of the FS-jumping ship threads I've seen are from landscape photogs that woefully wanted high MP, higher DR to help push their images further. Or simply fellow photo-"enthusiasts" that occasional sell a print here or there. This was the pre-5DS/SR days where canon had nothing above 22mp. (Canon stopped some bleeding from landscapers with the intro of 5DS/SR, but still lost the DR crowd to Sony/Nikon.)
I would say majority of the time, it's the bride-to-be that determines who the photographer will be. They will have looked through the portfolio for styling. I am generalizing a bit here but most women don't care how many megapixel, what brand, what model camera the photographer is shooting with. As long as the portfolio looks good (no chopped of limbs) and the photographer understands what they want during their special day, then the decision is made to hire or not. And they then expect the photos to look like those they saw in the portfolio. (contrast or the lack-of, high-key, low-key, filtered...)
I honestly haven't met anyone in the market for a wedding photographer that looked at a respectable wedding photographer's portfolio (without knowing what camera was used) and said, "Ah... see this set of photos... would have been much better with a Nikon." Or, "He/she must have shot this on a D810 because look at all that fine detail and dynamic range." They look for how people were posed, what kind of "fun" photos the groomsmen/bridesmaid took, artistic stuff that is dependent on the experience and talent of the actual person and not the gear. That's what sells a photographer's services.
In any case, for the time being, what little we have seen of the 1DX2 seems very promising. I would be very surprised if Canon holds back on the 5D4. Canon has never been shy to bring new tech to the non-flagship model. Just look at the 70D w/ dual pixel AF, which I think was the first to have dual-pixel (I'm sure someone will correct me if I'm wrong.)
The bigger question (for another thread perhaps) is what is Canon going to do between the 5D4 vs. 5DS2/SR2 once the sensor tech gets shared across. When that happens... will any wedding photographer choose the 5D4 over the 5DS2? I would think more resolution is always a good thing to have for such line of work. Can always resize down, right?