As mentioned in the Fedora bug, it would be nice to add a way to skip the migration dialog and directly merge the default config.
Possible options are: - Environment variable: XFCE_PANEL_MIGRATE_DEFAULT=1 - Command line option for xfce4-panel. For both cases I suggest to hide (and use the default) if no 4.6 config is found, so only the option exists for an empty or default panel.
Added XFCE_PANEL_MIGRATE_DEFAULT in a8a298a. Better to let the panel handle this instead of copying the default setup to the user's config directory.