I've been using Wayland for years and most applications will just work, either under XWayland or natively. The only problematic ones are the ones with incomplete Wayland implementations and the ones relying on the complete lack of security design on systems like X11 of Win32. The biggest blocker for me has always been Nvidia, and that problem was solved years ago. Meanwhile, whenever I drop back to X11, I'm reminded that things like multi-touch gestures are plainly broken on X11 mode in ever DE I've tried.

To be honest, I've never seen a Linux desktop that most people would call "production ready". Even in the best days, X11 and Wayland have glitches, hardware issues, and stability problems that no other platform seems to suffer from. It took until Pipewire for audio to actually work well out of the box.

As for X11, KDE and probably others will run X11 for years to come, mostly because companies like Canonical and Red Hat ship LTS versions. Whether applications will keep supporting old configurations is another question (what software still runs on Ubuntu 16.04? I wouldn't know and I bet neither do most third party vendors), but the protocol itself isn't dying any time soon. It's not allowed to by corporate contracts.

What is dying, is corporate investment into X.org and X11 targets for some desktop environments. Developers and companies that favor X11 can come together and fork those projects, or join the dev team, to ensure their desktops work like they used to. Just because IBM doesn't want to pay developers to maintain such configurations doesn't mean they suddenly stop working, just that someone else will need to apply bugfixes from then on out. The only serious attempt I've seen from people who want to keep X11 alive was that fork from that antivax anti-DEI weirdo.