I don't apply to this question...but I’ll turn it a similar way:
I am a New Yorker, who only follows the Knicks, but would also follow a second team like the Nets when they move to Brooklyn in 2 years. But that's only because I'm a bandwagon NBA fan, I don’t follow the NBA very much.
For the NFL, I am a die-hard Dolphins fan, and of course hate the Jets. But the Giants are my second favorite team (if I had to pick one)... just as the Mets are in baseball.
So I guess what I'm concluding is if another team moves to NY I would follow them somewhat if they were winning, so as long as they weren't a rival or in the same division of my team.