On the DOT an announcement was just made for the KDE 4 release schedule. Congrats to the developers and the team and everything.
April 1, 2007: Subsystem Freeze
From this date forward, no new KDE subsystem or major changes can be committed to kdelibs.
May 1, 2007: Alpha Release + kdelibs soft API Freeze
Alpha will be a source-only release without translations. The kdelibs API is “soft-frozen”, meaning that changes can be made but only with the consent of the core developers.
June 1, 2007: trunk/KDE is feature frozen
Trunk is frozen for feature commits. Internationalised string changes are allowed. A list of main modules that will be included in the final release will be made.
June 25, 2007: Beta1
Beta 1 is prepared and released after some initial testing. The incoming bugs will be reviewed for their severity. After this release, a new Beta version will be released every month.
September 23, 2007: Total Release Freeze
This is the very last date for committing anything that isn’t reviewed on the development lists.
September 25, 2007: Release Candidate 1
Targetted date for first release candidate. Only regressions (breakage caused by the KDE 4 port) or grave bugs can be fixed. Starting with this Release Candidate, a new Release Candidate will be put out every two weeks until the codebase is sufficiently stable and all showstopper bugs have been fixed.
October 23, 2007: Targetted Release Date