Allen Winter published an updated KDE 4.0.0 release schedule

We, The Release Team, hereby announce that we are extending the
KDE 4.0.0 schedule 2 months by inserting an extra 2 Betas, as follows:

September 24: Beta3
October 22: Beta4
November 19: Total Release Freeze
November 21: RC1
December 5: RC2
December 20: 4.0.0 tagged

We feel that there are crucial elements of the release that need more
development time. The feature freeze (less exemptions) remains in effect.

As usual, the dates are estimates and are subject to change.

-Allen, KDEPIM Release Dude