DPR has some pics up:
R5 looks good with a nice deep grip for larger lenses. 100-500 somewhat larger than the 100-400 though, seemingly noticeably fatter as well as longer
Canon shows off EOS R5, RF 100-500mm lens under glass at WPPI
Canon's upcoming full-frame mirrorless camera, the R5, is on display at the company's booth at the 2020 Wedding and Portrait Photography International expo in Las Vegas alongside the new RF 100-500mm lens.
www.dpreview.com
R5 looks good with a nice deep grip for larger lenses. 100-500 somewhat larger than the 100-400 though, seemingly noticeably fatter as well as longer