I updated and sddm-git replaced sddm-wayland-git automatically. However I still have the black screen and mouse.
EDIT: updated again with sudo pacman -Syyu --ignore egl-wayland. sddm is working great!
I found Ver 1.1.8-1 breaks plasma wayland. Sounds like this may be a nvidia problem.
EDIT2: Perhaps not able to resolve until October 11. When new Nvidia Drivers V495 will be available in beta.