A few things to keep in mind:
1-Any locale that is already part of an existing team's territory is a no go (San Jose and Baltimore). Existing franchises have moved into existing territories under unique circumstances. That happened in LA only because an existing franchise had nowhere else to go. It happened in NY because the Nets were already there as part of the ABA.
2-Talk of Pittsburgh, Cincy, STL, etc ignores the fact that these metros are full of other pro sports teams and the pie isn't big enough to accomodate another team. Bizjournals did a study a couple of years back. All you really need to know is that a mid-market or smaller metro with MLB and at least one other team is off the table. KC might be the only exception to the rule, but I doubt it. SEA is the minimum for an MLB+NBA+NFL team.
3-This leaves smaller markets who are the only games in town. When you look at the support the Spurs and Jazz get (even when they aren't so great), this makes a lot of sense.
The largest markets without pro sports (by metro total personal income) or territorial issues are: Columbus, Austin, VABeach-Norfolk, Vegas, Richmond, and Louisville. The first two have a huge college presence that takes away from support. VABeach-Norfolk-Newport News constantly fight over who gets the arena (and tax revenue). Vegas has the gambling issue. Unless the league looks outside of the US, Louisville makes the most sense by far. It would also resurrect a huge ABA rivalry (Pacers-Colonels). The Colonels were extremely popular and were actually doing better than a couple of the ABA teams that got in.
If there needs to be another team w/ Seattle, Louisville is the best bet.