Making geographic divisions not only aids attendance and viewership for newer rivalries, it lessens the amount of games teams like the Astros play on the west coast, where late games lessen TV viewership.
If they do add two team, I suggest Las Vegas and North Caroline, I'd like to see something like this:
East: BOS, NYY, NYM, PHI, BAL WSH, TOR, PIT
North: CLE, CIN, DET, CWS, CC, MIL, MN, STL
South: NC, ATL, TBR, MIA, HOU, TEX, KC, COL
West: SEA, OAK, SF, LAD, LAA, SD, AZ, LV
Games vs non division: 3 A vs half and 3H vs other half (flip each year): 3 games x 24 teams=72 games
Games vs own division: 6 H + 6 A vs 7 teams= 84 games
+ 1 game vs 6 in own division= 6 games
Or
play 4 games vs other divisions (can be 2H-2A or alt 4 H-4A each year for east-west coast trips): 4 x 24= 96 games
play 5H + 5A vs own division: 10 x 7= 70
play 2 games vs 2 teams with same place previous yr.= 2 games