What is the future of X.org if all the mainstream distros drop X11 for Wayland?

Retirement to the archives. The protocol is extremely dated and held together with duct tape. The maintainers are mostly also contributors to Wayland projects, where they are implementing features impossible with X11.

X11 is used in Xwayland

It is maintained by the same people and is on life support. It has been that way for a decade