You'll likely see a 300/2.8 in the R mount before you see a 400/2.8 or 600/4.For bragging rights they might do it someday. It won't be their top priority.
A 16-35 2.8 R and 24-70 2.8, 70-200 2.8 , 100mm macro and 400 and 600 R will be important to produce for the EOS R camera
The noctilux costs about the same as a 300mm f/2.8 w/ AF & IS, and would sell even fewer copies. Most Nikon photographers would rather pay quarter the price for the 58mm f/1.4g and gain AF on the way.Before Nikon's announcement of the new 58 mm f/0.95 Noctilux I would have said that Canon will not come up with such an extremely fast lens again. Zach Sutton's review of the old EF 50mm f/1.0 shows that Canon would have to improve the optical formula of such a lens substantially to make it fit for modern high resolving sensors. But because of the old rivalry between Nikon and Canon I wouldn't be surprised if they show off with a new anti Nikon super fast weapon for their RF system
I agree completely with you, Antono, but I think the old rivalry between Canon and Nikon had always a non-rational touch. But, maybe, Canon regards the new RF 28-70 F/2 as bold enough, since Nikon offers quite slow zoom lenses for their Z system. I am pretty sure that Canon will sell substantially more copies of that super fast zoom lens than Nikon of their Noctilux. Nikon isn't Leica these days, Leica can sell about 10 k$ prime lenses because they are established in the luxury market anyway.The noctilux costs about the same as a 300mm f/2.8 w/ AF & IS, and would sell even fewer copies. Most Nikon photographers would rather pay a quarter the price for the 58mm f/1.4g and gain AF on the way.
That is, the 58mm f/0.95 is mainly a show off. Canon would be better off giving the old EF 50mm f/1.4 the same upgrade it gave the 24-28-35mm trio. It would be cheaper to develop a 50mm f/1.8 IS USM, and it would sell a whole lot better.