Digicame-Info who aggregates rumors and information and typically has reliable information has mentioned today that the RF 800mm and RF 1200mm have been added to overseas dealers lists recently. This usually means that the lenses are very close to becoming available.
These lenses have been on our roadmap for quite some time.
According to Digicame-info;
There are rumors that Canon will announce the “RF 800mm F5.6 L IS USM” and “RF 1200mm F8 L IS USM” in the near future.
- Canon “RF 800mm F5.6 L IS USM” and “RF 1200mm F8 L IS USM” added to overseas dealers
Keep in mind, that this is the “usual” announcement period leading up to CP+ for Canon so new product announcements wouldn't be that much of a surprise right now either. Of course, we have had these two lenses on our roadmap for what seems like forever. (November 2020)
Digicame-info, notably did not quote and link the source of this rumor, something that gives me a bit of pause because they are very good at linking back reliable sources. That's not to say that this rumor is incorrect, just that it's a curious decision on their part.
The image shown is one of the Canon EF 800mm F5.6L
A patent doesn't prove anything, but it looks like it is possible it will be:
Patent: Is Canon planning to release catadioptric (mirror) super telephoto lenses?
And it actually looks like they have IS:
Canon RF & EF Lenses - rumours & news
Considering the size, weight and price of a "conventional" 1200mm F8 lens, it makes absolute sense to me if Canon made it as a mirror lens instead.
And they were definitely not inexpensive. I'd be surprised if Canon were ready to compromise on quality.
As a non-L lens, it would cost far less , of course. But who could handle such a lens, if not an experienced photographer, with the right (heavy) tripod?
As far as AF and IS, sure - because you have to have field correctors, and focusing elements on the back end of the Cat, and there you'd have your floating IS unit and AF motors, etc. Just like with a telescope you have your eyepiece coming out of the back of the Cat.
I really doubt it's a cat, I suspect it will be DO and be around the same size as the 800mm .. if you think about it, the 800mm F5.6 and the 1200mm F.8 will have roughly the same size as the front element. With DO, it would be smaller and around the same length as the 800mm.
That's my theory.