From a wildlife shooter perspective, I am not blown away. Unless Canon has significantly reduced size, weight, and price on the 400-1000 lenses, I don't see a significant advantage of RF lenses in IQ vs purchasing or using existing EF glass (other than adaptors). I have been in GTNP/YNP for the last two weeks shooting the R5/R6 and 100-400 f4.5-5.6 L IS II / RF 100-500 f4.5-7.1 L IS. While the extra lighter weight and 100mm additional reach is great, the image RF lens is only marginally better optically than the 100-400 II. The RF + 1.4x Extender requires zoom out to 300mm before adding the extender and the 420mm - 700mm is fantastic, but loosing the lower end of the zoom range is a significant issue if the wildlife is constantly changing the distance. You wither have to have a second body with the 100-400 II (which I did) or repeatedly having to add/remove the extender is going loose shots. I am currently using the R5 + 1.4x +100-500 for a 420-700mm with the R6 + 100-400 II to cover the lower range. The real solution hear would be switchable extender per the Canon patent, but you would still have to extend the lens before you could engage the extender.
If you already own the 100-400 II, I would consider how I use the lens and if I regularly need more than 560mm (EF lens + extender).
I would be blown away if Canon could provide prosumer options that meet or exceed the IQ and capabilities of the PF 500, Sony 200-600, and Sigma 150-600 AT comparable aperture ranges. I do not consider the DO f11 lenses a solution within 2 hours after sunrise and 2 hours before sunset. I tried the 800mm f11 and did not like the limits imposed by the narrow aperture and the DOF. I heave heard folks say at those ranges it is a narrow DOF, but compare the bokeh to a f4 or f5.6 L lens. I would have been very happy with an RF version of the 400 f4 IS DO II, 500 f4 IS DO and 600 f5.6 IS DO if priced similar to the 400 f4 DO II with the longer lenses.
David