The aggressive way Canon is developing incredible RF lenses that are way beyond anything Sony has even dreamed of or can do with the small mount will carry Canon through. Cameras come and go but great optics are far more difficult. Canon will have incredible camera bodies soon enough. Same pattern as the EF system that when completed totally dominated the market especially the pro market. I doubt they will just roll over and let Sony take the #1 spot without a fight. Nikon rolled over and quit by staying with the horribly antiquated flippy levers and whirly gears just to salvage the obsolete mount for "Legacy". when Canon destroyed them and they have never recovered, I doubt Canon will make the same mistake as Nikon didI think the gap may be closer than Canon would like - Canon haven't brought out a higher end camera since the 5dmk4, and I wonder how many people have started trying other options in that time where nothing new was coming from Canon.
The z7 doesn't seem to have changed nikons fortunes as such, so a new high end Canon may not be the 'be all, end alll silver bullet' to Sony's rise.