Try reading through this post... So between the learning curve, and the blackout between shots in a burst (ok it isn't a blackout, but it might as very well be, showing a black screen or the last shot taken has the same effect), it seems it is capable to an extent, but not the greatest tool in the shed for BIF. I expect much of the same during sporting events where players are constantly moving around in front of each other, and I would like to just track one player. The EOS-R supports the 3 sliders that lie under today's "AF Cases", but it doesn't seem to allow me to store more than one configuration and swap between them for different activities during a game.
I eagerly await the pro version, hopefully it is a sports oriented camera. After having shot the M50 over this past week, I love what mirrorless brings to the table for those times where I am relaxed and have time to think about my shot, or use manual lenses.
https://www.dpreview.com/forums/post/61778777
https://www.youtube.com/watch?v=8cRmyz-34Gg
I suspect you will like the camera more than you will dislike any shortcomings with it based on what you shoot.
Plus shooting at 800mm f11 with AF is a huge plus, something not very practical with the Canon DLSRs now.
It will be tough to buy the EOS-R for 4K usage that is for sure. This video shows some really bad 4K samples, some are saying that it looks like Canon is doing 2K and upscaling the video.
https://www.youtube.com/watch?v=3mUGuDXOTcA