Oh, I am certain that without a shadow of a doubt, Djokovic want to take that number one ranking away from Nadal. These are part of the key driving motives for him, he will want to reach that pinnacle just like Fedal did upon their return. The fact there is work to be done, will be a massive incentive for Djokovic to focus his mind, and fuel his hunger that much more. You can see just how bad he wants to win again, many matches he has won through sheer will power alone. Realistically, he knows that without some serious help from Nadal, he won't get year end number one, but what he can get is the USO and then use the indoor season as a catalyst to make a true assault at the number one ranking in the early months of next year.
Winning at Cincinnati, which was historically his worst event, has got to be such a massive boost. He can play much more freely, knowing he is gaining with every match, and when you have such a specific target, the work to get their begin to feel more like sprint. You can see the finish line, and you know every stride, and in this case, every match is getting you closer. Also, this is really now Djokovic season, this period all the way to Miami is his favorite time to hunt.
As for Federer, he really doesn't need the year end number one, even if he gets it, he only ties Pete at this stage. And his weeks at the top is miles ahead of Nadal and Djokovic, that should not be his priority now. For him, that is more of a case of been there done that. For Federer, it is about holding onto that slam record, the one he has, and the one the two want so badly to take away from him.