For Forbes, this is quite a poorly researched list. Both the Florida Marlins and SF 49ers have new stadiums coming in the next few years. The Marlins are moving down closer to Miami which should benefit them, and I believe the 49ers are building a stadium in Santa Clara.
As for all those NHL teams, both Nashville and Phoenix in brand new arenas. Nashville was also just recently purchased by an owner committed to keeping them in the area. And the Islanders? Are they kidding me? You'll never see a NY franchise relocate. I believe they also have a plan in the works to completely refurbish Nassau Coliseum and build a mall, bars, restaurants, etc. next to it, as well as access to public transportation. Dont know if that's been approved yet though.