That's right - he didnt. At wimbledon he was still ranked #2, and both those tournaments still were a part of his amazing run. He was still in a position where he can surprise everybody by making his year even more perfect. But this is not the case anymore - Now Novak is considered by many to be the one favorite to win any tournament, hence he has to fulfill very high expectations, which is something he never had to do before.
I do think he will win more than 5 GS titles. Around 7 is my bet. However, you do make a fair point there. I don't recall Novak defending any big title. I might be wrong, because I don't follow his career that closely. But I don't recall him defending his 08 AO and WTF titles for instance. Even at the Master Series level I am not sure if he defended any of his titles... I would ask Nole fans for that stat though.
This AO wil be crucial for him. It is not necessary for him to win it, but he will need at least to go deep into the tournament. Federer after his 2004 season didn't win his two first GS of the year, but at least made semi-finals and had a brilliant run at the US hard court season winning both titles at Miami and Indian Wells.
Since I am not neither a fan or a hater of Nole I consider myself neutral on those issues. I do like the guy's game though. Last year was amazing for him, but Nole had issues with consistency in the past. This year will put his resolve to the test. Sure he was the fav to win the USO, but it is a totally different ball game becoming the undisputed number one after a great season.
He is the new king of tennis. However, sooner or later his mother's infamous words will come to haunt his own son ... lets see for how long this king will be alive.