In Short: Facebook is currently testing a new redesign of the Messenger application, and that design has surfaced on Twitter, including a rather detailed look at the dark theme that is coming to the app. If you check out the gallery down below, you will be able to see 12 screenshots combined in two images, and those screenshots are showing off various menus from the Messenger app in both light and dark themes. As you can see, it's not a huge revamp in terms of the design, but the bottom bar will be much cleaner once this design lands, while basically every submenu has been redesigned, some more than others. Icons are different in this version as well, and the app looks cleaner in general, though not necessarily what some of you would expect for an Android app, as it's not exactly following Google's Material Design guidelines, though that's not that surprising considering this is Facebook's apps. The dark mode brings a completely dark background, not dark gray, which will look great on AMOLED displays.
Background: Facebook first announced that this redesign is coming back in May, back then, the company said that the redesign is coming to iOS and Android, but did not specify when exactly, the company only said: "in the near future". Well, it's October already, and the redesign still did not arrive to users, well, at least not all of them. A report surfaced at the end of last month claiming that the update is rolling out to some users, but it seems like Facebook opted not to test this update with a lot of users, as not many of them received it.
Impact: Dark mode seems to be a rather popular move by app developers lately, especially Google, who has pushed out that option to a number of its applications lately, Facebook will follow with its messenger application soon, it seems, but we still do not know when will this update land on your device, even though it'll probably arrive within a month, but surely before the end of the year.