Does anyone know when IPv6 will be available for drop-in mode?
This is currently open as feature request FBX-16907. There isn't a tentative release version for this feature yet, so there isn't a date that I can provide.
If you'd like to follow this feature request, please create a support case and mention that you'd like to track FBX-16907. This way you'll be updated automatically.
WatchGuard Customer Support