Canon may yet be serious - I suspect we haven't seen the body those lenses were made for... A couple of rumor sites are saying "something high resolution will come out before Photokina in May". It'll be interesting to see if it uses the recycled 50 MP sensor from the 5Ds, or something that deals with the dynamic range issues of that sensor?
I'm purely guessing here, but I think the second body may have been meant to come out in the initial release. On the other hand, a senior Canon executive (in the same interview that he hinted at the high-res body) also said something like "remember the 50mm F1.0 EF - we put that out to show we could, it was very high end for the initial EOS bodies". Of course, there were many more lenses in the initial EF release - 12 in the first year, only one of which (the 300mm f2.8 ) was at all exotic. The 50mm f1.0 came along a year or two later, around the same time as the EOS-1 (according to Wikipedia, the 50 and the EOS-1 were both 1989, but they don't say which came first.
How would the many Nikon fans on this thread feel if the initial release had excluded the Z7? Nikon happened to have a sensor that was an excellent fit for a high-res body (adding PDAF to the D850 sensor may not have been hard), and they made the decision that it was cheaper to use the high-end Z7 body for the Z6 as well than to build a "prosumer" body. The Z6 could have very easily gotten its own, D610-grade body. If that were the case, either body could have fallen behind the other in development...
I wouldn't be surprised if Canon has two cameras waiting for us at Photokina? How about an "EOS-R1" and an "EOS-R1s"? What if they share a body that addresses many of the complaints about the EOS-R? The EOS-R1 would have the best AF system yet seen in mirrorless (and competitive with the EOS-1Dx mkII) and a maximum frame rate of 12 FPS or more on a sub-30 MP sensor. The EOS-R1s would lose a lot of the frame rate, but pick up a sensor in the 50 MP range. The challenge is that Sony and Nikon have set the going rate for a high-resolution body in the low $3000s, and Canon may well want to charge more than that for the fast body. They could follow Sony's example with the A7rIII and the A9, going against years of their own pricing policy with any EOS 1D and Ds variant, and make the fast body more expensive than the high-res variant, they could add enough features that they at least try to put the high-res body close to 1Ds territory, or they could just price them similarly ($4500? - the high-res body would need something that clearly set it above the Z7 and A7rIII).