It is not uncommon for some of the top players to not play in any tune-up tournaments leading to a grand slam, especially during Wimbledon season when its lead-up is just very short. And I guess, Novak Djokovic wanted to have sometime out of the spotlight after losing in the French Open final.
He does appear to be more relaxed now, more confident, I just hope fatherhood hasn't dulled his killer instinct, especially during the most crucial moments of a championship game. That we would know once again as I still pick him to be the player to beat on his side of the top upper half of the draw.
Probably, his most difficult possible match-up would be against Kevin Anderson, who played well this grass season. Kei Nishikori still has to prove himself in grass. Other possible tough opponents for him would be two Aussies, veteran Lleyton Hewitt and Bernard Tomic. Anyhow, Novak should get the semi-final berth on his side of the draw.