It's rumoured that the upcoming full frame mirrorless camera from Canon will have a 30.4mp sensor, which is the same resolution as the EOS 5D Mark IV. It's also been said that the camera will be an “EOS 5D Mark IV without a mirror”.
We've now been told by a couple of people that this will not be the case. The 30.4mp sensor (which we haven't confirmed with certainty) will be “very different than what is found in the EOS 5D Mark IV”. We would expect as such, as marketing a new mirrorless camera with a 2 year old sensor would be extremely difficult and would give a presumption that the camera would be “dead on arrival”. Simply removing a mirror from a DSLR that one might actually own isn't the kind of sales pitch that most Canon shooters would embrace. In an ideal world, Canon would like you to have both cameras in your kit.
We're also told that the camera will have an articulating screen, which isn't found on the EOS 5D Mark IV as well as the latest DIGIC processor. Dual SD card slots are also highly likely. One source has claimed that the camera will have DPAF 4K (pretty obvious), but that the crop will be “significantly different” than what is found on the EOS 5D Mark IV.
We have an update on an announcement date. We're told that Canon will have announcements the second week of September from a very good source, this contradicts the previous post that we'll see announcements in the first week of the month. It is highly possible that Canon will have multiple announcements ahead of Photokina, as we're expecting a lot of cameras and lenses to be announced around that time. Photokina begins on September 26, 2018.
Please take all of this with a grain of salt, as the information coming in is quite vague.