The Canon EF 600mm f/4L IS DO BR USM lens was previous announced at Canon EXPO in September 2015. Now according to CR, this lens will be officially launched at the second half of 2017.
Along with the new Canon DO super telephoto lenses, Canon is also working on updates on several super telephoto prime lenses, with weight saving, updated coatings and IS systems and more. We may see these updates in 2018.
via: CR