According to latest rumors from CR, Canon currently is testing some super telephoto DO lenses, these DO lenses are:
- RF 400mm f/3.5 DO IS USM
- RF 400mm f/4 DO IS USM
- RF 500mm f/4.5 DO IS USM
- RF 500mm f/5 DO IS USM
- RF 800mm f/9.5 DO IS USM
Only one of these lenses will be go official, the most likely DO lens will be RF 500mm DO lens. This lens may coming along with upcoming flagship full frame mirrorless camera EOS-R1, which is expected see a development announcement at the end of this year.