It's doubtful that they'll pick Nashville as they don't really have any thing set up, same with Charlotte. Nashville became the sexxy pick, even though if you look into it their effort is far behind that of Utah and Portland.
Realistically, if they decide to do an east coast and west coast, I think it's between Portland/Utah and another city out east. But imho thinking they have to go east/West would be stupid, because west of the Mississippi , MLB has 11 teams (and west of Colorado there are a *total* of 7). There are 10 teams within 600 miles from Nashville, for example, and there are zero teams within 600 miles of Seattle. Hell, the closest MLB team to Seattle is (Sacramento) is still over 700 miles away.