Kde 4.3.1 was silently released and kubuntu packages can be downloaded from kubuntu-ppa/backports
All Kde dependent packages on my PPA and backports PPA were just rebuilt against new KDE 4.3.1 packages on kubuntu-ppa.
I wonder where did they get it, because I couldn’t read any news about the release anywhere.
EDIT:
I found the announcement! http://www.kde.org/announcements/announce-4.3.1.php
But there is no link on Kde homepage…
EDIT:
Finally the announcement is also on http://www.kde.org