Nothing like a mirrorless rumor to get the forum juices flowing.
A few thoughts:
1) I'm skeptical about a full-frame mirrorless Canon rumor. People always ignore the fact that Sony is a niche player in the camera world. They went all in on mirrorless simply because that was the only niche available to them – they could not compete against Nikon and Canon in the DSLR market. It was the only route available and the market statistics that we have access to would indicate that they haven't been all that successful. Sony market share is flat.
2) I've always said that if Canon were to go mirrorless full frame, it would use the EF mount. Nothing magical there, just build the body with sufficient spacing to allow for EF lenses.
3) I used to think that an effective viewfinder was critical to the long-term success of mirrorless. But, I have to admit I am beginning to doubt that. Dual pixel autofocus, touch-screens, improved tracking and face-recognition software make a viewfinder less critical. Plus, there is the fact that the vast majority of pictures being taken today use cameras that don't have viewfinders. With each passing year, we have more and more people who have only used a rear screen. People who will only know cameras that use rear screens are being born every day, while people who use viewfinders are dying every day.
4) For me personally, the only mirrorless that has any appeal is the Fuji X-Pro series and that is mostly because they are cool looking. My ideal mirrorless would be a fixed lens 15-90 mm APS-C in a classic rangefinder retro-style.
5) All the strongly expressed opinions on this thread only confirm something that I've observed every time the subject of a mirrorless Canon interchangeable lens camera comes up – what Canon releases, it will satisfy 10 percent of the people on this forum and the other 90 percent will be convinced Canon is doomed because they didn't build exactly the camera they were hoping for.
6) The most interesting aspect of this rumor is this:
...the camera will use a newly designed 24mp full frame image sensor.
Interesting because, if true, it almost certainly means the 5DIV will use the same 24 mp sensor.
We finally know an important specification for the 5DIV.