According to CR, Canon is going to update two new super telephoto prime lenses in 2018. Canon has already updated 4 new super telephoto prime lenses in last several years, first the EF 300mm f/2.8L IS II & EF 400mm f/2.8L IS II came, followed by the EF 500mm f/4L IS II & EF 600mm f/4L IS II a few months later.
One of these two lenses could be EF 600mm f/4 DO IS lens, this lens has already shown on Canon EXPO in late 2015.
There is no detail on the other super telephoto prime lens, stay tuned for more info.
via: CR