See also the "main to-do list". All dates given here are subject to revision, but we will try our best to stick to them if possible. The KDE Technical Working Group is acting as release coordinator for the 4.0 releases.
Targetted date for first technical preview, mostly a developer release.
The kdelibs API will remain as stable as possible after that, so that application developers (in particular those not having their code in the KDE SVN) can start porting towards a stable kdelibs API. Of course the applications in the KDE SVN will have been ported all along, and it will possible to alpha-test them at this stage.