I don't know but I think it should be easier than in 2009. He didn't take a long break then, but he didn't have too much time to practice either, then he had the stomach problems at the US Open. Now he'll come back at the beginning of the season and if he starts practicing this week, as planned, he'll have plenty of time to get in shape.
He also said he wants to feel 100% ready before stepping on court. Playing exhibition matches at the beginning should also be helpful.
Winning AO seems a bit too much, but I wish people would stop acting like he's a hard court mug.