If Nate thinks that wayland only on Plasma 6 is the way to go then I feel like we as a user should trust him.
Well… that is not what he is saying. X11 will be supported for a long time still. In fact KDE has not even set a deadline for ending support for X11^*^. It will definitely not end with the release of Plasma 6.
The point is that not adapting software to Wayland is a mistake. It may be a pain, but X11 is virtually abandonware. The developers have moved on (to Wayland) and there are no new versions coming out – unless someone forks it, of course, but that would probably be another mistake, as the codebase is an unsustainable mess.
This implies that, yes, when most software projects have got their applications working on Wayland, X11 will be phased out as a platform Plasma works on, but there is no date for that yet.
– ^*^ Other projects are less coy. Fedora is considering removing support X11 from their very soon, maybe in their next releases. This is what sparked the discussion. Not KDE.