Alexander Iliev, the current Xfce4 XKB plugin maintainer, sent a message to the goodies-dev ML telling that he is looking for a new maintainer for xfce4-xkb-plugin. Please get in touch with him if you are interested.
xfce4-xkb-plugin currently has 38 open bugs on the Xfce bugzilla, 4 of them have a patch in bugzilla. This plugin to switch between different keyboard layouts has a lot of users, so you'll make a lot of happy users if you start working on this! Xfce needs you!