I received some information on two upcoming/rumored Canon RF lenses:
Canon RF-S 33mm f/1 L USM lens: there is already a patent for such lens (P2021-167921A).
Canon RF 70-300mm f/2-4 L IS USM: 1.6kg zoom lens that still has a large aperture of f/2.4 at 150mm. The image quality at 300mm should be equal to or even better than the already discontinued Canon EF 300mm f/4L IS USM lens.