We know that Canon is bringing a lot of new RF mirrorless lenses to market fairly soon, and it looks like we have more information coming in, with some exciting news on new designs.
We recently heard that RF versions of the 400mm f/2.8L IS and 600mm f/4L IS are on their way soon, and now, there is news about the RF replacements for the 300mm f/2.8L IS and 500mm f/4L IS. Canon Rumors is reporting that those two lenses will likely be coming in early 2022, with some improvements over their EF predecessors. Namely, the 500mm f/4L IS will likely be much lighter and shorter than the EF version (which likely points to the usage of diffractive optics). Furthermore, the 300mm f/2.8L may appear as a zoom lens. Such a lens is not unheard of. Sigma currently makes the 120-300mm f/2.8 Sport, which is probably my favorite lens I own, as it just so remarkably versatile compared to a supertelephoto prime. My copy has found uses ranging from baseball to concerts and much more. Nonetheless, Canon Rumors is reporting that a prime version is also in development, so it isn't yet clear which one will make it to market (or if both might). It looks like the next year or so will be quite exciting for Canon fans!