Canon will announce some of the following RF lenses this month. The 300mm and 500mm will come early next year.
- RF 100mm f/2.8L IS USM Macro
- RF 300mm f/2.8L IS USM
- EF 400mm f/2.8L IS USM
- RF 500mm f/4L IS USM
- RF 600mm f/4L IS USM
Frankly, I doubt these big white lenses will be a best seller unless Canon announce the top-of-the-line EOS R1 mirrorless full frame camera soon to go with them.
Even then, many serious and professional photographers will find it hard to justify buying another series of big white lens after spending tens of thousands of dollars acquiring the Super Telephoto EF series.
Speaking for myself, I have the EF 100mm f/2.8L IS, EF 70-200mm f/2.8L IS III, EF 300mm f/2.8L IS II, EF 400mm f/4L DO IS II, EF 200-400mm f/4L IS 1.4x extender, EF 500mm f/4L IS II, EF 600mm f/4L IS III. It will be the last thing on my mind to replace all of them with the new RF series version. I simply do not find the incremental 'improvement' of the RF over the EF series make any economic sense.
For those starting their Super Telephoto inventory from scratch, it is a different story but for established photographers, it is a hard sell, at best.