The KDE SC packages have been updated to the latest stable version available: 4.13.3.

The packages have been adapted to be used with runit and ConsoleKit, and support suspend/hibernation, and fast user switching.

To install it and enable KDM:

# xbps-install -Sv kde
# ln -s /etc/sv/dbus /var/service/
# ln -s /etc/sv/kdm /var/service/

A screenshot of my KDE desktop: