Interesting. Don't have an R so I have no idea how in practice it is a real issue. You would have to have a crazy fast subject for it to change direction enough in a half second or what ever it really is for it to really impact tracking. Just me, but my solution for the issue would to be just to shoot a little looser - back out 10 to 20%. The R is a 30 mpx camera, right? So lets say you are shooting 20 percent looser to compensate for the delay in response, that would give you the same as shooting with a 24 mpx sensor after cropping. That is still a lot of resolution and you've created a buffer for change in direction. In my experience it shouldn't keep you from getting the shot..... that said, you have a 30 mpx camera, you would like to be able to use them all... so I get the annoyance.
The flip side to that, is the two events I shot this weekend, I rarely chipped after getting my initial setting dialed in. And I've usually done that before the event starts. It's kind of funny - one of the events I shot was on TV - so my wife watched from home. Evidently I was in the background of the a lot coverage, and my wife asked me when I got home if I ever lower my camera from my eye. Getting real time images in my viewfinder has all be erased the need to chimp, and I can keep the camera at the ready more often. So its a give and take thing. Maybe you loose a fraction of a second between frames, but you gain not needing to chimp.
Each has its nuances you learn to shoot around. I'll have to play with the R sometime to see what it really is like. I have the feeling it is a lot like shooting the original 5D or 20D back in the day... but with the advantage of full frame focus and meeting coverage. Maybe kinda nostalgic.... but then again we got great images from too.... we thought the Mk IIn was the bees knees for a long time.