Where they go will probably be determined by how old they are. The younger free agents will go where the money is. LA and Boston will have less money to offer than a lot of teams. So I believe the younger free agents will sell their services to those teams with more cap space, whether they are good teams or not.
The older free agents, especially those who have already made their mega-millions, will want to join Boston or Los Angeles. A title will be more attractive to them than $. That's my opinion, anyway.
But really, it won't just be Boston and LA that will contend for the next few years. Cleveland, Atlanta, and New Orleans have a chance to be right up there. Cleveland has a good nucleus to build around, all they need is to make smart decisions and find the right pieces. Same with Atlanta. New Orleans is almost there. And really, the Spurs just need to find some younger legs (but not too young and inexperienced!) to help them get back to contention.
Boston is not guaranteed to be in a position to contend next year. First, they'll have to find a back up PG, regardless of what happens in this series. I'm hoping Ainge will take a look at Calderon, and dare I say it, Vujacic for our back up PG next year. He'll have to avoid resigning Pollard, Cassell, and House to free up some money. I would think that PJ, Posey, and Calderon will give us a very solid 8-man rotation. LA should be fine as long as Bynum comes back healthy.