My last few stadiums have been based on this study from Beyond the Box Score, exploring the likelihood of expansion into major cities:
Part 1: The Top 10 - a list of the ten most likely expansion cities.
Part 2: The Underdogs - cities that are less likely to have a major league team, but fell within the parameters of the study.
Part 3: The Dependents - Cities that had factors that could make or break them.
We now have parks for the top 20 most likely expansion locations (including multiple options for a few cities) in the study. So, feel free to expand away.