We don't yet know the finalized specifics of what the 2020 MLB season will look like, assuming it comes to pass. However, we do know that a larger playoff field is highly likely.
In the expanded wild card era, MLB has handed out 10 postseason berths per season -- one to each of the six division winners plus two wild card bids per league. For 2020 (and probably beyond), MLB is probably going to grow the field to seven playoff teams per league. Such a revised postseason structure was already under consideration even before the COVID-19 shutdown, so don't be surprised if this one sticks beyond the 2020 season. Reportedly, here's how it would work:
Seven teams from each league make postseason (14 total);
The team with the best record in each league gets a wild card round bye;
The two other division winners and top wild card team host all games of three-game series in the wild card round;
Those two remaining division winners get to pick their wild card round opponents (during a live broadcast) from the three other wild card teams. The top wild card team plays the unpicked team;
Three series winners and the team with a bye advance to divisional round.