Canon still owns the space, it's theirs to lose.I don't believe the "professional base" is worth as much as one might think. This is an industry in steep decline... especially the sports photographer and photojournalism base. The wedding and portrait photographers don't have much call for an R1. That's a much bigger "base", though also in decline.
If the R1 can't best the A1 or even their own R5 the Agencies, Leagues, Teams, Magazines, TV Networks, Digital Media, Colleges and every photographer is not transitioning away fron every 1DXMKIII, II and I out there.
Thats a BIG built-in Canon base to start with even before SONY, Nikon shooters decide to switch to Canon.
I generally will start with two new bodies and get a third for a kit and glass optimized for same.
If each photographer and their associated entity does the same.... Like I said..... Canon will make billions. It's Canon's game, field and ball. Why would they not enjoy the money? Relative to today's matket... It will be "dominence" and that is what Canon wants to maintain as the leader in global sports photography.