2018 is the world cup & winter Olympic games year, according to CR, Canon is planning to update two new super telephoto prime lenses in this year. The focal length of these two new big white lenses is unknown yet.
One of these two big white lenses could be EF 600mm f/4 DO IS Lens that already showed back at the 2015 Canon Expo. The other lens remains a mystery at this time. Stay tuned for more info.