CriteriaWe should consider size, both in terms of television market and population. TV markets are important because larger markets can mean better deals, which means more money, which means more money to spend on players or to fatten owners' wallets. Arenas are requirements, too, although an expansion franchise can be obtained simply with a promise of a new stadium. History is important as well, although less so: some cities are eager to regain teams while others simply can't keep them.
SizeIndianapolis is roughly 25th in TV market size. Fortunately, many cities above them have teams, but several do not, including Tampa-St. Petersburg (significantly larger), St. Louis, and Pittsburgh (both slightly larger).
In terms of city size, Indianapolis is much bigger, 12th overall, with only San Jose and Jacksonville both larger and without an NBA team. However, looking at metropolitan areas, Indy drops to 34th, with only five NBA cities smaller (Milwaukee, Memphis, Oklahoma City, New Orleans, and Salt Lake City). The three larger TV markets, plus Cincinnati, Kansas City, Las Vegas, and Columbus, are all larger areas. (Baltimore is also larger and separate from Washington; it's unlikely that a team could move that close to an existing team. The Nationals were in a different situation, having been ruined by an incompetent owner and in desperate and immediate need of a place to play.)
ArenasThe St. Louis Blues play in a multipurpose arena that can seat 21,000 for basketball. The Tampa Bay Lightning arena can seat 20,500; the Penguins' place holds 19,000, and the Shark Tank can hold 18,500. Kansas City has a relatively new 18,555-seat place with no regular tenant.
Cincinnati has an aging arena that seats 17,000 and is unlikely to be NBA-worthy. Jacksonville's new arena seats only 15,000, and while it's much newer, it's also small enough that it likely wouldn't be a viable place to play (especially in a city that can't fill an NFL stadium). Columbus has an on-campus arena that seats somewhere close to Conseco's capacity, but I'm not sure that's a viable option. Las Vegas still has the Thomas and Mack Center, but while its capacity is not an issue, there's a little detail that has yet to be resolved to the NBA's satisfaction.
HistorySt. Louis had an original NBA team and had another team that is still active, plus one that lives on in perpetuity.
Pittsburgh had a BAA team that didn't even make it to the NBA, as well as a short-lived ABA team, so there isn't as much history there, and of course Tampa has never had a team.
Ironically, both Cincinnati and Kansas City not only had an NBA franchise, but it was the same one, and it's likely to be on the move again.
The other cities never had a professional basketball presence.
ViabilityLas Vegas is completely out until the gambling issue is resolved: after that, they'll be completely in, but I'm not sure whether the NBA wants to be the first one to embrace gambling. Jacksonville, Cincinnati and Columbus don't really have good places to play, at least not for an existing franchise. It's unlikely an owner would take an existing team and move it to a similar market with a worse arena.
Kansas City has an arena with no real conflicts, but I'm not sure there's much of a difference moving there (unless you count it as revenge for Indy taking the NCAA headquarters). San Jose has the size and an arena, but the Kings and Warriors have both been moving here and there during their California histories, and even the Clippers took a brief look around before settling into the Staples Center. There's definitely money in Silicon Valley, but perhaps not enough to support another team.
That leaves Pittsburgh, St. Louis, and Tampa-St. Pete. The first two would be slight upgrades in TV market size and metropolitan area, but I'm not sure the interest is there (although they might help to pay back the city for helping to build the Penguins' shiny new toy). Even Tampa isn't an obvious winner. Although it's a much larger market, both in TV and population terms, it's also in a fair-weather state (meant literally rather than in sporting terms) with two existing teams. Florida isn't exactly supporting three NFL teams, it's not quite supporting two MLB teams, and there are questions as to whether any NHL teams can survive down there. A third NBA team is probably not a great idea.
So ...There are a lot of options, there are a few reasonable options, but there's no obvious choice. Then again, the Sonics moved to Oklahoma City because someone wanted them to, and the Hornets moved to New Orleans because
Now, if there were any billionaires in Tampa who had experience owning franchises ...
 No lie. $14.57 million per year simply for stepping out of the picture ... not that they made that much at the time, just that they bet well and won huge. (return)