One motivation for the proposed versioning scheme change is precisely to separate the API of the underlying platform from UX changes.
There are — to the best of my knowledge — no plans for a big architectural change to the desktop like when gnome-shell replaced metacity and gnome-panel in GNOME 3.
That doesn’t mean that the UX isn’t going to evolve of course, but it really doesn’t make much sense to version it like API. Anything that would be released as “GNOME 4” would be much closer in terms of UX and technology to 3.36/3.38 than 3.36 is to – say – 3.10 (no wayland, no headerbars, significantly different desktop shell).