We don't have a script in order to migrate translations.
However, Falang propose their services for custom projects so you could probably ask them to do the migration for you:
www.faboba.com/en/prestations.html
Honestly, it's been more than a year that Joomfish say that they are working on a new version for joomla 1.7 then 2.5. So far, it's still not available. Plus, staying on Joomfish doesn't mean that you won't have any data migration to do to the new version as it is apparently a complete revamp.
If you are not afraid to have to wait for half a year, you can wait for joomfish. Otherwise, I would go with falang.