It's a possibility, but I don't see it happening.
First, if Lebron wants to move on, this is the year to do it, as there are a lot of teams attractive to him that have cap space. Teams like the Knicks, etc., might not have that space in a year.
Second, I've got to believe that Lebron wants long-term security. Nobody knows how the next CBA will affect player salaries, so I've got to think that Lebron will take the best contract he can now.