I wouldn't take that chance for anything other than our own #1 next year and an expiring AB. No way I'd use a potential high pick. It would be lunacy to give up a BRK or LAL pick for him.
People can theorize that he would want to be in Boston, but there's no guarantee getting to LA isn't more important to him, no guarantee that we won't have a mediocre season next year, and no guarantee Lebron won't blow up CLE and entice PG to LA (or elsewhere) with him. Once we make a deal for him, he holds all the cards. Would be monumentally stupid by ainge, but then that's his specialty.