The big battle MariaDB (or any DB) is going to have is gaining ground in the shared web host space. That makes up a pretty large portion of websites, and there is no incentive for those providers to change. I'd love to see other DB options in that space, its all PHP/MySQL.
That'll probably happen - mainly because the distributions will probably switch over to MariaDB. I'd expect Ubuntu, Debian, CentOS etc to all ship MariaDB as an upgrade at some point.
