there are several missing entries in several xfce packages, attached list should be pretty complete wrt trunk. I'm using Xfce general product/component here, because goodies (apps and plugins) as well as core packages are affected
Created attachment 2033 missing POTFILES.in entries
Considering we went into string-freeze since this bugreport was opened. And we have successfully released a RC... this bug can be closed :-) (Thanks for the effort though Christoph)