While it was originally thought that 20 was the ideal number of MLS teams, Garber said that the league plans to add four more teams by 2020, bringing the total to 24.
Since the beginning of the 2005 season, the MLS has added 10 teams.
“The strength, passion and vision of the MLS ownership group is the foundation behind the success of our league,” Garber said in a release. “We look forward to adding new partners with the same commitment to the sport and love of the game.”
Source: Evan Hilbert, CBS Sports MLS Plans To Expand To 24 Teams By 2020 by Blake Bass