I really can't call this one. Surely an injury or surprise retirement would lead to an amnesty (like we used the last one on Vin Baker's buyout deal to get it off the cap), but I don't see Paul just getting cut because he's not in the plans.
I also don't think I can see Paul wanting to leave Boston to ring chase. He already has one. It's not like Ray Bourque. But, on the other hand, I could see him passing on a rebuilding year to play for the Clippers for a year or two, but I doubt it.
I think the C's will keep him around no matter what. He has value to a rebuilding team if we go with young players. It's not like contenders are the only teams that need talented, versatile veterans. He has value if we do actually land a top FA, too. So the most likely scenario is that he stays for at least most of his contract, barring injury.