Xfce 4.2 is now available in Arch Linux repositories. Please have a look at http://www.xfce.org/ for the official announcement.
This release brings 3 new packages: xfce4-session, xfce4-icon-theme and xfce4-appfinder, and deprecates xfce4-themes and xffm-icons. After a sysupgrade, make sure to perform the following operations to get a full-featured Xfce desktop :
pacman -S xfce4-session xfce4-icon-theme xfce4-appfinder
pacman -R xfce4-themes xffm-icons
Some people have reported issues with KDE K menu loosing its icons after Xfce upgrade, so please make sure to have libxfce4util 4.2.0-2 installed. For more details, see task #2028 in the bug tracker (http://bugs.archlinux.org/)
And last, but not least, many thanks to Tobias Kieslich for his very nice artwork contribution to these brand new Xfce packages.