According to the Mysql documentation, there is no table or database boundary.
The underlying file system may have a limit on number of directories .
Engines can have an individual value, such as InnoDB that allows more than 4 billion tables.
What can occur is slow, due to the number of existing tables, but limit does not exist, depending on the storage engine.
Also note that this is a bad practice, of course, depends on the application, but I do not see any need to do this, seeing that the programming language itself with a good modeling in the DB can resolve it in a cleaner way and efficient.
See more at Limits on Number of Databases and Tables