Qt 6.0 Alpha was released two days ago. It is now making it's way into the KaOS repo. It will stay in kde-next only for the foreseeable future, since nothing can use it yet.
But it is time to get ready for the this move, KDE Framweorks should start to move to Qt 6 fairly soon, so better to get the build issues for a new major Qt out of the way now.
All Qt PKGBUILDs are converted to CMake right now, so quite a bit of work until all is done and working correctly.
So Qt6 will be coinstallable alongside Qt5 right?
Yes, and the beta is being build right now.