If LeBron extends his contract, I get the feeling Wade and Bosh will as well.
Why? Because they're all buddies, which is why they set up their contracts the exact same way. The goal was for 2 or more of them to sign with the same team and dominate the NBA. If one of them decides to stay put, I'm pretty sure that the others would follow suit.
This would seriously fuck up New York, Jersey, etc