Almost immediately after the announcement of the Canon EOS R camera and RF mount, Canonites and others were already wanting what was coming next.
Now, the Canon Rumors community likely qualifies as a fairly advanced camera consumer. Unfortunately, the Canon Rumors community isn't the majority of Canon camera buyers and I think enthusiasts can lose track of that from time-to-time, it's not a slight, it's just a reality of the camera business.
A great source and I had a conversation recently about the future of the EOS R system, and mostly about what camera(s) to expect next. The source simply lead the conversation with “follow the money”.
And what does that mean?
Simply, do not expect any sort of “niche” or “professional” mirrorless cameras prior to the release of more “entry level” products. A $4000+ camera simply doesn't move anywhere near the volume that a sub $1500 camera would and at the end of the day, Canon needs more RF lens mount equipped cameras out there. So yes, we expect to see a model under the EOS R before we see any sort of high megapixel or “professional” full frame mirrorless camera from Canon.
A different source said similar things recently and swears that an APS-C EOS R body is coming before a “professional” full frame mirrorless shooter is.
For now, expect a lot of RF lens announcements and one sub $1500 USD full frame mirrorless camera from Canon before you count on and EOS-1D X Mark II equivalent mirrorless body.