A few weeks ago, we saw a few users get a new redesigned version of the Facebook Messenger app which was a bit more material than it was before. Including a floating action button, as well as a flat design and tinted status bar. It's a great looking update to the messenger app, and now the material design version has leaked yet again. Showing us that a few more people are getting the update to the material design version. The redditor that posted the screenshot is in the beta, and according to the comments, it looks like a few others have gotten the material design update already.
We have installed Facebook Messenger here but do not see the material design that you see in the screenshot above. So it appears to be a server-side switch for the app, and for those that are in the beta. Similar to what's happening with the Instagram app and multiple accounts (it's a server-side switch as well as being in beta). So if you aren't seeing the update to Facebook Messenger, you should be seeing it a bit later on, although that all depends on if Facebook is planning on sticking with this redesign. But it is a great looking design for the Facebook Messenger app.
Lately, there's been talk of Facebook as well as Facebook Messenger killing the battery and performance of Android smartphones, while this is likely true, it is still great to see Facebook working on these apps to make them better. With their CEO, Mark Zuckerberg wanting to get 50 billion people using Facebook by 2030, he's going to need to have his team working on his Android apps, otherwise that target is going to be a bit tough to reach, especially if Android continues to grow like it has in recent years.
To take part in the beta for Facebook Messenger, you'll need to join this Google Group, then follow the directions posted there to opt into the beta. It's not difficult at all. And once you opt in, it could take up to 2 hours before you are actually seeing an update to the beta version of Messenger.