Take a look at the list of upcoming lenses
http://thenewcamera.com/upcoming-canon-ef-lenses-2018-2019/ Canon EF 400mm f/2.8L IS 1.4x / 2.0x TC
Replacement for the EF 800mm f/5.6L IS
Canon EF 600mm f/4L IS 1.4x TC
Replacement for EF 800mm f/5.6L IS?
Canon EF 200-600mm IS w/1.4TC
superzoom lens for FF / APS-C DSLRs
Canon EF 14mm f/2L
A faster replacement for the EF 14mm f/2.8L II?
Canon EF 50-300mm f/2.8-5.6 IS DO