The reason I chose Oakland and Seattle to be the ones that move over was to help preserve rivalries. The Rangers/Angels, Rangers/ Astros, and the Dodgers/Giants are traditional rivalries that I intended to keep intact.
The A’s moving to the NL West also works as they already have a built-in traditional rival in the Giants. This is perhaps the most promising case of rearranging divisions for the Rockies. With this, they have an even split of sea- and middle-elevation-based games, meaning that the schedule can be more easily worked out to help the team succeed.
Finally, MLB will expand eventually. When that happens, the league will increase to at least 32 teams. Divisions will probably mirror that of the NFL, with the number of teams in each division decreased to four.
In theory, they could make each division eight teams, but for this, we will assume four per division. People expect these teams to be one much further West than Colorado (Las Vegas, Portland, Vancouver) and further east than Missouri (Nashville, Charlotte, Montreal). Unless the league throws a curveball and puts a team in San Antonio or Oklahoma City, the Rockies scenario looks the same regardless of the MLB’s choice.