It seems to me like such a drastic change in the underlying system (removing support of one of two major display platforms) would mandate a major version change.
Complete removal of X11 should be an event to trigger KDE 7.0.
I agree. IMO this is a breaking change. It seems like some (many?) accessibility tools don't work on Wayland, so this breaks users' workflow if they need those tools
Complete removal of X11 should be an event to trigger KDE 7.0.