Comment 5 for bug 684664

That should be very easily cacheable in principle, though it could be complicated with existing code structures. The exporter is checking whether the template (the whole template — it's just picking a POTMsgSet as a sample) is XPI or regular gettext. If it's XPI, everything's a bit different: the singular text (what gettext calls the msgid) then needs to be retrieved as the English (“en”) translation instead of simply as POTMsgSet.msgid_singular.