With all the news coming out with this Chris Paul situation, I now believe even further that the Celtics are the most likely destination for him if he were to be traded. New Orleans HAS to trade Paul, there is no way they can't if they care about their basketball team. (Which its owned by the NBA so they are going to care about making money off of it.)
It's clear that Paul wants to be in New York, so alot of teams with younger talent right on the cusp of being competitive will shy away from a deal with him because they'd be in fear of losing him. Main example: Would the clippers really be willing to lose Eric Gordon for Paul who would possibly leave after the year? Probably not. Specially when they have two decent PG's already in Bledsoe and Mo Williams. Also see: Golden State (Stephen Curry.)
The Celtics are in the best position because no matter what, if they keep Rondo or if they get Paul, after this season they will be in rebuilding mode anyway with a whole crapload of cap room to go after free agents. The Celtics, with a third team involved are going to be able to willingly offer New Orleans the best package because they arent mortgaging their future for possibly a one year plan in Paul and shipping off Rondo. (This part is opinion because I don't believe Rondo to be a cornerstone of a franchise, rather he is just a good piece of a puzzle)
Even if Paul won't sign an extension I think the Celtics should do the trade anyway. Paul gives the Celtics the best chance to win a title this year as his scoring abillity takes so much pressure off of the rest of the starters. He is also a good playmaker, is not a good of off ball defender as Rondo but I believe he is about just as good as an on ball defender. I think the biggest difference it makes is rebounding on the offensive end. Instead of teams being able to clog the paint, they'll have to help onto Paul, helping clear the paint and make offensive rebounds easier to come by.
Trade for Paul for the year, try and convince him that Dwight Howard is a true possibility for next year and maybe he stays. If not, maybe you can convince Deron Williams and Dwight Howard to team up. But the best deal for Boston is to trade for Paul now so if they were to extend his deal; they can go as far over the cap with his deal as they want because he is their player. They sign Howard with him, and get Ray/KG to sign on for vet friendly deals and you are contending again.