Canon Watch has added two new lenses to the RF mount roadmap for 2021, claiming some one of a kind telephoto and super-telephoto lenses are coming for the RF Mount.
First up, an RF 250mm f/2L IS USM. This sounds good on paper, but I don't think 250mm is a focal length consumers would understand, especially those that are currently using the EF 200mm f/2L IS USM, which is my favorite Canon lens by the way.
Second up, an RF 500mm f/2.8L IS USM. I'm no engineer, but this would be a massive lens. We have not yet seen an optical formula patent for this yet.
The third is the long-rumored RF 70-135mm f/2L USM. I have been writing about this lens for a while now and it continues to get mentions.
Take this info for what it's worth, but I guess anything is possible.