Ok, so Xfce 4.4Beta2 has started to be uploaded to Debian. If you can, wait before upgrading, only core Xfce has been upgraded, not the plugins. So they'll have to be removed when libxfce4util4 will be installed and libxfce4util2 be removed. Plugins will be uploaded asap (maybe tonight), so wait for some days more to be built and added to unstable.

In the meantime you can upgrade using my repository, or just wait. Beware that xfce4-mixer is currently broken in unstable due to the rpath fix. A fix will be uploaded today.

You can follow packages to be uploaded here.