I've been using Linux long enough that I was around for KDE 3 and KDE 4. I did not enjoy using them, but I love 5. I'm nervous about this upgrade. I can't think of anything I want that would merit a major version upgrade.
A. 3 -> 4 required very very significant changes. 4 -> 5 and now 5 -> 6 are nowhere near that.
B. KDE really learnt their lesson on this and they are very careful not to create anything similar to that. Thus, not big rewrite/changes like 3 -> 4 are in the works.
This is just to get the whole project going with Qt 6 which isn't that much different from Qt 5.
Edit: Disclaimer, I used to be a very minor contributor to KDE around 3 -> 4 time.
Good to hear KDE 5 is doing fine at least, let us hope for the best.
I get that many people are more excited about rewriting stuff than fixing bugs but oh man is the risk is rarely ever worth it. If you have a good thing going, don't kill your golden goose.
Now that software is starting to mature again (at least in my mind, and at least with open source projects), changes are more welcome. Watching updates is more interesting because the bullet points look interesting from a utility standpoint rather than a drama standpoint.
The reason is pretty straight forward. If you break something at that level you tend to break almost everything, and people have spent a lot of time building stuff on top. Shaking that in a big way is always risky. People tend to be more conservative the more you go towards the bottom of the stack.