This issue has some history:
I made a pull request 4 months ago, including a input tag for making django-cms be able to get current language: cf4be06
You stated that would be better to include a tittle into the span, as a better solution to having a hidden element.
But this other solutions needs django-cms js plugin to be changed.
Just now i have seen a pull request which does the same:
Related to #69
This patch adds the title field to current span, and I have a django-cms pull request ready to be sent, which will add suport to get language from current span title (Also fixes another django-cms issue for language).
Maybe we should apply both solutions: the #69 for old django-cms instances to work, and this current span titlte for doing things well :).
Adds current language code for django-cms plugin editor
This pull request fails (merged f2451f6 into 8c5b05e).
As far as I know, this should be fixed in #69.