If Djokovic continues with the form he showed from Wimbledon onwards this year, it really is difficult to see who is gonna stop him. He will be heavy favorite in every slam barring the French. And even the French he will still have a shot at. The young guys like Zverev, Shapavolov, Chung, & Tsitsipas show promise, but still appear unable to break through yet. I don't really see Federer challenging him on any court or Nadal for that matter barring the French. This only really leaves the likes of Cilic, Murray and Wawrinka. Murray though appears finished. Wawrinka has shown he has the tools, but has done nothing this season. Barring injury, I expect Djokovic to win a minimum of 2 slams but more likely 3.