Beside Djokovic, Murray and Wawrinka as slam contenders, we will have recovered Federer and Del Potro, improved Raonic and Nishikori, and maybe even Rafa who may have better clay season.
Looking forward to 2017 B-)
I think the only people who saw Novak's loss in ATP finale finale with more pain than I did were Federer and Nadal. I think that ever since Djoker went to dance with sugar plum fairy they contemplate big return in 2017 and I won't be surprise if they accomplish so.
I think if Djoker doesn't manage to go back to his old ways quickly and wins AO, Federer will. I also expect Nadal to be factor again during all the clay season. Perhaps not to win all the titles, but still some and play RG finale win or lose.
Each time Del Potro went to top 10 he had bad luck with his wrist. I don't think there is a big chance he will have more luck next year.
Raonic and Nishikori may have 2016> 2017.
We may see more from young guys, first of all Thiem, Zverev and Kyrgios.