I'm of the belief that a team doesn't have true "fans" until they have been in one place long enough for children to have grown up going to games with their parents and then take their own children to games. There is nothing you have to prove to the second generation of fans in order to have their loyalty -- it's all they've known since childhood.
I'm from Birmingham originally, and we don't have any professional teams aside from the White Sox AA affiliate which no one cares about (except for when Michael Jordan was learning he can't hit a curveball there). Most of our pro teams have just died with the ill-fated leagues that brought them there in the first place:
- The Americans of the WFL played one year (won the title!), changed names to the Vulcans, and were declared the champions of the league's final year when there wasn't enough money to hold playoffs.
- The Alabama Vulcans joined the AFA in its third year and folded after one. That league stayed around long enough for the Alabama Magic to form, play one season, and fold without actually paying the players.
- The USFL came to town the next year with the Birmingham Stallions, which lasted three seasons before the league imploded horribly, having spent a lot of money that it didn't actually get from the networks.
- The NFL made the Birmingham Fire one of the founding franchises of their WLAF, and then moved it to Germany two years later when they decided that all the teams probably needed to play on the same fuck*ng continent. I'm not sure Europeans actually care about the leage, but the NFL has boohoodles of money so it's staying around.
- When the CFL tried to expand into the USA, we got the Birmingham Barracudas for a season before they realized Americans don't care about Canadian leagues, and the CFL did not have the boohoodles of cash necessary to support it until we did. I am told they are in posession of approximately one third of a boohoodle. Is this true?
- The XFL had the Birmingham
Blast Thunderbolts (the name changed when someone realized the Birmingham Blast was a church bombing that was a pivotal event in the civil rights movement) for one year, but the league collapsed under the weight of Vince McMahon's steroid-fueled ego.
It's really nice to have a team that is local to you. Even if you don't go to the games, you probably know someone who did. You're reasonably certain you can strike up a conversation with strangers that relates to the team, even if it's "How 'bout those Eagles, eh?" Only twenty years ago it was very difficult to find information about teams that weren't local, because "sports news" was basically 5 minutes on the TV news and two pages in the paper. Now, if you have a satellite dish you can watch just about every game played by any team in any league if you want. I like the Packers and the Bengals for no real reason, but I can follow them just as well as someone in their city from whereever I happen to be. It's kind of cool.
As for the original post... I kind of doubt the Blazers in particular will be leaving, because just about every team there is has done the "we're leaving once our lease is up" dance and most stay where they are. That said, basketball teams are also the most mobile franchises in our three major sports, so what do I know? I just don't get how, say, Charlotte was so horrible for the Hornets but is suddenly just fine for the Bobcats, or how the Oilers drew under 10,000 for their last games in Houston but suddenly everyone loves the Texans forever. Eh.
Also: the NBA could probably support another team or three (to get it to even numbers), but they're better off going slow rather than expand recklessly like the NHL did. I'm betting if the Hornets return to New Orleans there will be an expansion team in Oklahoma City relatively soon.
PS: I am sorry about the rambling.