Bulpett has some good insight on this:
http://bostonherald.com/sports/celtics_nba/celtics_insider/2013/06/rivers_still_leaning_toward_return_but_hes_intrigued_by-"Multiple sources insist the odds are still "overwhelmingly" in favor of Rivers continuing on his current contract, which still has three years and $21 million left."
-"Another insists Rivers is angry at reports he is at odds with Danny Ainge over the direction of the Celtics as they try to rebuild on the fly."None of what's happening now is tied to Paul (Pierce) or Kevin (Garnett) or any of that," he said. "There's always been a very good relationship with Danny, and that's one of the biggest reasons why he'll still probably come back."
-"Rivers is also said to be intrigued now by some of the high profile jobs that are -- or could be -- available. such a change of address would require that team providing compensation to the Celtics, who clearly see Rivers as a valuable asset. "