According to recently rumors on CR, a loose Canon RF mount lens roadmap for 2020 has been shown to select photographers, and the plan is to release between 6 to 8 new RF mount lenses in 2020.
Canon has already announced 4 RF lenses now: They are RF 28-70mm f/2L, RF 24-105mm f/4L IS, RF 50mm f/1.2L, RF 35mm f/1.8 Macro IS STM. And there are already two RF lens patents: RF 24-70mm f/2.8L IS, RF 24-300mm f/4-5.6L IS. Canon already mentioned in their announcement video that they are working on “a series of fast f/2.8 lenses and more”. Which means we may see these new f/2.8 zoom lenses in 2019 to 2020.