He'll let Crean stumble through the next election, handing another victory to Howard and biding his time in NSW. When Howard passes the baton to Costello after the next election, he'll make his move. Costello will be wildly unpopular, of course, given his sneakiness and his general smarminess, though he is actually a very intelligent man but then so was John Hewson.
Carr is a sneaky, slimy and incredibly efficient political player. He really knows how to think strategically, shaft the right people and grease the way when he needs to get through. He's also good at identifying hatchet-men to take on his dirty work, Costa being the current (contrast with Howard's Wilson Tuckey and fall-guy Reith), while remaining clean himself.
In short, the NSW Right can and will be the place where the next Labor Prime Minister emerges. Sad but true. At least we'll know what to expect: economic "rational"ism, greenwashing, lip-service to liberty, tough-on-crime etc etc