The current plans for a port to Qt6 and KF6 are for the moment focused on porting away from deprecated APIs and we are trying to resist the urge to do any bigger changes. Hopefully this will make the transition easy. An overview of all the small tickets is available here: https://phabricator.kde.org/tag/kf6/
Over the years, y'all have gotten good at this as a developer community, and this adds to my confidence. :)
I'm sure the constraint is frustrating in some ways, but you've built a desktop experience worth conserving as you advance it!
I guess Qt 6 is out now, and so Qt 5 will soon be unsupported if it isn't already. I wonder how the balance of rewriting and breaking API changes will work out for the Plasma 5 to Plasma 6 transition! Here's hoping the KDE devs figure out how take advantage of the opportunity for helpful/necessary API changes without having to cut or reimplement too many features. What users have got at present is really, really nice