The next time expansion will come up is in the next CBA which should be around when the Rays and A's should have their stadium issues either cleared up, settled or have moved. The A's and Rays could eliminate two of the cities that MLB is looking to expand to so that is why expansion is currently on hold. MLB wants to expand and will expand once the Rays and A's stadium situations are solved for. The A's look like they will be staying in Oakland and the Rays look like they are on their way out.
In the scenario of the A's staying in Oakland that open ups Vegas as a city and that will be the west coast team. Depending on where the Rays go (Charlotte, Nashville, Jacksonville or Montreal) that leaves one of those four cities getting an expansion team. I think the Rays go to Charlotte which leaves Nashville and Montreal as option 1a and 1b. This will all depend on who can get a good ownership group and a stadium bill passed. I think if Nashville gets a MLB team then the Sounds will move from Nashville to Montreal with MLB paying the bill for this.
If the A's move to Vegas and the Rays move to Charlotte then I think Nashville and Montreal get teams. If the Rays and A's both stay then we could possibly see 4 new teams. Las Vegas, Austin, Nashville and Charlotte/Montreal would be the four cities that get teams which then the MLB would be more like the NBA 17 teams in each league and no divisions with the teams divided by geographic location.
With 34 teams I think this is what MLB realignment would look like.
AL:
Yankees
Red Sox
Blue Jays
Mets
Phillies
Pirates
Nationals
Orioles
Reds
Guardians
Tigers
Marlins
Rays
Nashville
Charlotte
Braves
Astros
NL:
Cubs
White Sox
Brewers
Cardinals
Rangers
Las Vegas
Austin
A's
Diamondbacks
Rockies
Dodgers
Padres
Giants
Twins
Royals
Angels
Mariners