I hope Djokovic continually works on his serve(he had it in a good place, then he fucked with it, and now it's finally starting to get close to where it used to be). After this USO I think he shows that he has the game to play with the best in the world, but he needs to work on harnessing his emotions to play well all the time. he's so up and down and that's his biggest problem. He can either look like a joke who deserves to be ranked out of the top 100, or he can look like the best all-around player in the world.
Hopefully DelPo gets his wrist back in order, he could dominate the hardcourts for the rest of his career with how big his groundstrokes are. If he can tweak his game and get a bigger serve maybe we can see him challenge for Wimbledon, but he'll have to find his old hardcourt form first. I don't see him getting far on clay courts for awhile, unless he really works on control and high spin instead of his big booming flat strokes.
I think Murray has been on a downhill slide since everyone got him hyped on AO/Wimby/USO this year. As much as I dislike him, the more people we have seriously contending for majors, the better for the long term health of the sport.
Nadal will probably take time off so that he can work on extending his career as much as possible. He's been getting a lot better at going for more winners, but every once in awhile when he can't beat somebody easily, you see him go back to his grinding form. If more players begin to challenge him like I think Djokovic can, we'll begin to see him deteriorate faster, so it's to his advantage to take as much time off as he can.