I reached out to Moiz yesterday to see if he has a mock showing how the dropdown will look once it's expanded and how the dropdown will be closed.

Change 292992 had a related patch set uploaded (by Jdrewniak):
T131526 A/B test on wikipedia.org

https://gerrit.wikimedia.org/r/292992

Change 292992 merged by jenkins-bot:
T131526 A/B test on wikipedia.org

https://gerrit.wikimedia.org/r/292992

Analysis is completed - this task is done. Here's the summary of the results of this tests:

One of Discovery’s Wikipedia Portal team’s goals is to make wikipedia.org a more inviting experience. One thing that worried us, from a user experience perspective, was the large section with links to Wikipedia in all the different languages. Specifically, we were worried it might be overwhelming to a new user. To that end, we propose a design change wherein that section is made optional and redesigned to have a cleaner, columnar layout.
We ran A/B test to assess the effect of this change for a week, from 6 June 2016 through 14 June 2016. The test group consisted of 3019 users who received the cleaner design while the control group consisted of 2560 users who received the current design.
We found that the test group had a 3.64% higher probability of interacting with the page and was 1.07 times more likely to engage with the page than the control group. Furthermore, although both groups received the dynamic primary link feature, users in the test group had a 6.82% higher probability (1.09 times more likely) of visiting a Wikipedia in their most preferred language.
Our main goal with this design change was to decrease the bounce rate (increase the engagement rate). We saw a significant improvement in how people engaged with the page when given the cleaner variation, which suggests that we should proceed with this change.

sorted by most articles to least by language

This sounds like "Make it hard to find the only language that I read". Have you considered just alphabetizing instead?

As a thought exercise, imagine that you need to put your mailing address into a web page. Think about how much more difficult it would be to find the name of your country, if the list was sorted by the size of the country.

Hi @Whatamidoing-WMF,

Thanks for your input - we've been kicking around the idea of using an alphabetical language list, rather than the listing by article amounts.

I've created a ticket to run an A/B test on this idea and if it tests well, we'll need an ok by the community to implement it, as I'm not sure how many folks check the portal page to see where their favorite language is in the list by articles.