Here an article from Biz Journals that talks about the most overextended v. the most ripe markets for new markets.
It only covers US markets, however.
In any case, it comes with a spreadsheet covering every MSA and which ones would have ample income for new teams v. ones that do not.
I suggest for baseball if you were looking at a smaller area, that combining metro areas would work too.
You can download the database
here.