I don't know about that. There are instances when the resolution bump is important for sports people too. The mechanical shutter speed of 12 fps is really the comparison point, as sports shots really do suffer from electronic shutter jello effect. There will be times when 12 fps disadvantage isn't as great as the 20 megapixel disadvantage of the 1d3. Lots will depend on other things, like buffer depth. Still too early to tell.
It can help, but it's way down the list for me, and can be lived without. I've run a lot of deep crops without it. Durability, initial target acquisition, consistency are all much more important.
I've owned 6 1D bodies for sports for myself and other photographers. We've put outrageous quantities of shots on them as sports tournament photographers. Some of them hit well over a million actuations. Only the 1DmkII (non-x) wore out, and that one was heavily used before I got it. In my 1DX/1DX2 bodies, I've never had a shutter replaced sooner than 450k clicks (usually it's longer than that), with one exception, and that was a bad sensor from the factory (which has been spotless since). They only get replaced because they're already at the lab for fixing, and it might be another 200-300k before there's time to send it in.
They've been dropped, exposed to elements, been in all sorts of temps and just keep on ticking. Only failure was a faulty rain gear letting water pool inside and shorting out the LCD screen. Camera still worked great, just had to go semi old school.
I'm more excited for the R6. The 7D2 was a brilliant value, because it gave you 80% of a 1DX for 1/4 (or less) of the price. It also provided a 112-320mm kit that could cover any field sport for about $1400 for second shooters. But it was not capable of great, only good to very good in terms of image quality. The
Canon R line, while painfully underpowered for sports, produced a stellar image when it nailed the shot, and locked on crisper than any of my five 7d2's ever have.
Surely there will be some corners/rough spots that the R6 suffers from, or there'd be no reason to buy 1Dx3/R5 (or the eventual R1X). But if it can bring the focus precision of the 7d2 with the mirrorless functionality, I will run to trade in my 7D lineup for those.
I'd love to be surprised, but I highly expect all three to maintain the current classes. And that's perfectly fine with me, because portrait/videographers do not need my battleproof tank, and frankly sports shooters can get by without it. And I'm not about to buy a fleet of them, or the company goes out of business
But what's exciting is the possibility of actually using the 5R confidently for sports. The frame rate of the 5D was the dealbreaker.