It was inevitable that Canon would be bringing at least one big super telephoto zoom lens like the EF 200-400mm f/4L IS USM 1.4x to the RF mount lineup, and this patent unearthed by Keith at Northlight Images shows Canon is working away at such lenses.
USPTO Patent US20220035144 shows the following optical formulas.
Canon RF 150mm-600mm f/5-6.3L
Canon RF 200mm-400mm f/4L
Canon RF 200mm-500mm f/4L
Canon RF 300mm-800mm f/8L
The designs contain a lot of elements, so these are definitely “big whites” and not more affordable lenses.
I could definitely see Canon releasing more than one of these types of lenses in the future, perhaps alongside the Canon EOS R1.