Since 1998, the MLB has been filled with 30 teams spanning 17 different states, in addition to a team in both Washington DC and Canada. However, commissioner Rob Manfred stated that he is open to the idea of adding another team. As he sees the MLB as a growing business, he sees expansion as a type of natural progression.
Although no bids have been made yet to host a new team, several markets seem viable, including Mexico, Montreal, and San Antonio among others. Nothing would be established for a few seasons, although the groundwork could be laid for another team or few. It is also possible that teams could relocate if they see a better market than their current one. Perhaps during this upcoming offseason more talk will come out of this possibility.
See this map of who baseball fans root for: