According to CR, along with upcoming Canon cameras, we will see at least two new super telephoto lenses coming for the Photokina 2018.
According to CR & NL, Canon recently has filed several new telephoto prime lens patents at the USPTO. The range of patents are from 200mm to 800mm.
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.