I really don't know what to think about this camera. On the one hand, I really dislike the body design - if it's supposed to be a mirrorless version of a 5D Mark IV, it just doesn't reflect the beauty of one. It looks more like a prosumer body to me - in fact the closest comparison is that it looks like the Canon EOS 650; the first EF-mount camera that Canon released in 1987 - so perhaps Canon was going in that direction, and body style will evolve over time as we get into the pro bodies. To me making a mirrorless equivelent of a DSLR pro body was one thing that Nikon really got right with the Z, but this camera, at least in the images I've seen, just doesn't look like it is at the same level/caliber.
I'm also not sure who this camera is aimed for. It's got one memory slot - an SD card slot at that - so just like with Nikon Z, I am sure that "pro shooters" - especially wedding photographers will come out saying that this camera will not suit their requirements. SD is far more failure prone vs XQD, so that may introduce issues as well. The camera appears to be more aimed at video shooters, yet we do not know if it will crop the video or have rolling shutter issues like the 5D Mark IV.
For photographers, the camera is missing the dial wheel - something that I've grown to love on Canon bodies. It's also slow - as slow as 5fps with servo AF. At the same time, the AF point coverage sounds incredible. And the lenses also look incredible - especially that 50mm f1.2. But, the fact that this camera uses an adapter, as opposed to EF mount (as discussed on these forums) is quite disappointing. I'm still hoping that Canon does decide to release a version of this camera that natively accepts EF, but it may be impossible.
I would say that going to a new mount after 31 years is quite a big move, and if its the case, I certainly hope that Canon provides necessary details about the adapter performance, and reasons as to why it was necessary to go "RF" in the first place and what are the advantages.
Ultimately, I think this camera's success really depends on price. To me, it has to be under $2K given what it has and what it doesn't. Over $2K, and suddenly I'm not sure who this camera is for. On the other hand, if Canon nails it with video, providing uncropped 4K video with C-log, they may have a winner.
Perhaps one last thing I would add: I feel that with this camera, Canon is still very much holding back in mirrorless, and holding on to DSLRs. This just doesn't feel like a genuine attempt to getting into the mirrorless field. But then again, I may be completely off-base with this - ESPECIALLY when I consider the Canon EOS 650 - that too was not a pro body, or a pro camera. So perhaps what we have here is a genuine rebirth of the 650 in mirrorless format, and we will see the pro bodies to come in the future?