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). <a href="http://www.kde.org/announcements/announce-4.1-alpha1.php">The feature freeze is in place</a>. 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.