It is, but Mint has always prided itself on adopting new technology late once all the dust has settled. Besides, it's just for Wayland being the default (and most likely deprecating the X11 session), a usable wayland session for cinnamon will most likely be available come 2025.

There's always POP!_OS going in hot with their COSMIC compositor, so people who want to adopt wayland can do so when POP!_OS does and still have that "Ubuntu(TM) experience minus Canonical" distro.

If you want to see a hell of a wait, you should check out RHEL's deprecation timeline.