lebron is going to Jersey when his cavs deal is up with jay z
No, he's not.
LBJ has made it very clear that playing for a winning franchise is important to him. If he wanted to be in NJ, he wouldn't have signed the extension with Cleveland before last year. Not to mention, with the NBA's CBA the way it is, the Cavs can offer him more money than anyone else.
The Nets (or Knicks) would have to be pretty bad to have the cap room to sign James. LBJ is not going to join a bad team in his prime and then wait three more years for that team to build. That would be like Tom Brady leaving NE to join the Oakland Raiders because his friend owns part of the team.
The whole small market of Cleveland vs large market of NYC argument with regards to LeBron is laughably outdated. With the global media we have today, there is not a single extra person on this planet who would know who LBJ is because he plays for the Brooklyn Nets as opposed to the Cavs. He also likes the fact that he's close to his family, and he's setting up some roots by building a mega-house just outside of Cleveland.
One team which will be in very good cap shape in 2010 is the Spurs, and I don't know if they'll still be "good" then, but I think LBJ may give that one serious consideration if the Cavs don't surround him with a winning team.