It looks like Canon will begin shipping the Canon RF 800mm f/5.6L IS USM and Canon RF 1200mm f/8L IS USM on May 26, 2022 in limited quantities, which is likely fine because I imagine these will be purchased in limited quantities.
Canon RF 800mm f/5.6L IS USM Key Features
Outstanding Image Quality, 800mm Super-telephoto Fixed Focal Length Lens
Expands the EOS R System
Impressively Light at 6.9 lbs., While Retaining High Levels of Image Quality
Minimum Focusing Distance of Approx. 8.53′
Optical Image Stabilization with up to 4.5 Stops of Shake Correction
Three IS Operation Modes
Super Spectra Coating (SSC) and Air Sphere Coating (ASC) Helps Minimize
Ghosting and Flare
Compatible with Canon RF1.4x and 2x Extenders
Customizable Electronic Focus Ring, with Manual Focus Capability during SERVO AF...