The Columbus media market is just a bit too small for an NBA franchise to exist here. We are already the 2nd or 3rd smallest market (depending on surveys..and Winnipeg doesn't really count for this purpose because while it is small compared to a US market, this is Canada, and a large market for Canada)for the NHL, keep that in mind. Also, while there would be immediate interest and a full arena early on, unless the team starts to win early, interest would wane rather quickly, maybe even more quickly than it has for the Blue Jackets. Plus, the NBA fanbase here in Columbus is much to aligned to the Cavs and the rest fans of other city's teams (like me, I am a Celtics fan..born and raised in Boston).
Although I completely understand what you are saying, I will point out that columbus does have a larger media market than milwaukee,indy,new orleans,oklahoma city,and memphis at least according to arbitron,all of which have current nba teams. You could also make the argument that other cities that do not have nba teams are alligned with other cities franchises primarily because they have no one to root for in their own city.I also think that there is no way to determine if interest would wane if the team started to lose. In my opinion columbus was much more of a basketball town compared to hockey prior to the bluejackets and I would also make the argument that stars on opposing nba teams are much more of a household name and would be more of a draw then nhl stars.
Columbus would have the benefit of not only having a nba ready arena and infrastructure but also being in close proximity to pittsburgh and the basketball hotbeds of cincy and kentucky.I'm not saying it is going to happen but columbus is one of the few cities that could make a easy transition for a relocated team.
I also agree that columbus will not ever recieve an nfl franchise but I would argue that it has more to do with the proximity to cleveland,cincy,indy,detroit,and pittsburgh and less to do with media market.There are currently 6 cities in the nfl with smaller markets.