Is that good? I know that the two are compatible right now, but I worry a bit that MariaDB goes in one direction and MySQL in the other and I'll have a problem.
Does concrete5 stick with MySQL in the future or are there plans to migrate?
Future incompatibilities are only going to be for very subtle configurations or for unusual/obscure usages, not things that concrete5 interfaces with.
There's no actual 'migration' needed to change between one or the other, the connection to the database is abstracted away, while queries are still all pretty common/vanilla.
Are you using it?