Blackcoffee17, I think you hit the nail on the head. The big news in Canon Land is that its limiting factor is now officially sensor readout speed. And, my, what a limitation it is. My personal use case would drag it down to 3 frames per second, making my SL1 look zippy. The fact that it is coupled with factors such as focus priority and servo focusing seems to indicate that it is also competing for limited processing resources on the same chip (onto which Canon is loading all sorts of new computational tasks with new, nifty features). We may see them divvy up the chipset into some purpose-specific ASICs, which would hopefully sort the problem, but that's not as quick a fix as it sounds, as it likely involves changing the architecture.
Upshot: R looks promising; not usable for an action shooter; will be if Canon can offload readout to a fast enough chip, but maybe not as soon as we hope.
Do remember that Sony introduced a bunch of readout-speeding changes when it launched the A9, giving it the capacity to suck down about 500mb per second in readout. This isn't easy stuff. It's highly invasive to sensor design, so it's not like you can just add on a chip and call it good. If Canon wanted to have 10 fps with the 5D4 sensor in their new R mirrorless, they'd have had to introduce sensor changes *because* of the readout, and this product management decision would have taken place more than a year ago. That may well have happened after the A9 came out. If so, it would be consistent with a 5d4 sensor appearing first with lame FPS and Canon jst being late as normal with the newer version of the sensor. That's my hope. Would mean we might expect something competitive sooner than later.