The Growth team has strong relationships with Czech and Korean Wikipedias, and we are newly bringing in Vietnamese Wikipedia (per the work on T206159). These relationships help us deploy features, test them, and learn from those communities. We will eventually want relationships with additional wikis because (a) we may want to broaden our ability to experiment and (b) if we find features that increase retention, we will want to deploy them to more wikis.
Therefore, one of our 2018-2019 Q3 goals is "A fourth, larger community beyond Czech, Korean, and Vietnamese is participating in conversations with the Growth team in their own language."
Thinking about how quickly this process unfolded with Vietnamese Wikipedia, we may be able to do more during this quarter than just start conversations -- we may get all the way to deploying features. We want this fourth mid-size wiki to be larger than any we already have, and therefore we are thinking in particular about Arabic or Persian. Those languages are also right-to-left languages, which would be good to add to our work.
Our team's Community Relations Specialist will primarily be driving and defining this task.
Since Q4 2019, a budget exists to have more paid Community Ambassadors. The relation with this wiki benefits this advantage.