It has been recently announced that Bitbucket will be leaving Mercurial support in 2020 , defaulting to Git from then on.
A lot of things come to mind when reading the announcement, mostly because Mercurial has been my first distributed revision control system or at least the first one I understood. It's fairly simple to use, concise and with a simple interface, but sadly has fallen in popularity.
Git has won in other fields where popularity is more important that correctness and simplicity. If I would go back in time and choose between Git and Mercurial, I would still choose Mercurial, it's still a great tool.