Comment 2 for bug 1207442

Yes, we should have a guideline.

It is best to update PO files automatically if there are translatable strings updates, but it is not automated now.

For temporal solution, it is acceptable to me that any backport with string update must comes with message catalog update (It makes the patch larger. One line change comes with tens of message catalog updates.
Another option is to update message catalog in stable branch manually periodically (or short before the stable point release).

Regarding translations, there is no official way to update translations into the stable branch.
Though it is not a scope of this bug, we need to have a guideline taking both of these topics.