KDE 4.0.0 has been tagged in KDE's repository. The next step is that tarballs are created and distributed around the world for packagers who will then create packages for their platform (Linux distribution, FreeBSD, Solaris and what not). So the release is imminent.
Before you try it out (remember, it is a double-zero release), I'd like to point you to Aaron Seigo's blog:
http://aseigo.blogspot.com/2008/01/talking-bluntly.html. It explains in detail what you can expect and why.
Have fun!
Uwe
