It would be good if we could change the sister project descriptions into the user's language.
Related to T135759: Wikipedia.org Portal: investigate getting translations for 'the free encyclopedia'
and the recent additions to the footer at https://www.wikipedia.org/ (per https://lists.wikimedia.org/pipermail/wikitech-ambassadors/2016-May/001409.html )
(Note: I only tested how it currently works, by changing the dropdown language selector, and then reloading the page. Possibly it does translate already, via different loading routes)