The KDE Team has released the first Alpha of KDE 4.1 which should be the version to replace the 3.5 series (that even I'm still using). The feature freeze is in place. 4.1 will be able to run on any operating system including Windows.
Hopefully they will be able to iron out the bugs for the forthcoming Kubuntu 8.10 release. I believe community development should rest in the 6 month Ubuntu release cycles since it is stable. The community still needs to work out how to easily install software (like a Mac) without using a package manager. I believe that the Mac puts all its dependencies inside a 'folder' that the program uses when it runs.