I'm neither a huge Djokovic fan or Federer fan (although I'd go Federer if given the choice), but I'd like to see Fed's 17 stand up.
I know it's easy to fall into the trap of looking at current results and projecting them forward indefinitely, and perhaps that's exactly what I'm doing here, but it just seems increasingly likely that Djokovic is going to catch him.
He just has a lot going for him. Two of the four majors are played on his best surface. Nadal isn't putting up much resistance anymore outside of the French (and he's fading there as well). There aren't any current dirt ballers who look poised to poach French Open titles in the same way that a Sergi Bruguera, Guga Kuerten, Carlos Moya, or Gaston Gaudio have in the past. Although he's doing his darnedest to prove otherwise, you also have to figure that Fed isn't going to be at it very much longer.
Above all else, it's just tough to see who is going to emerge to challenge him on a regular basis. Murray is the first name that comes to mind, and I think he still has some majors in him, but Djokovic has largely dominated their H2H. Stan has two majors now, but he still flames out relatively early in draws to feel all that comfortable that he's going to become a guy anywhere close to on par with what we've seen from Fed, Nadal, and Djokovic over the last half-decade.
Also, let it be known that the biggest negative if Djokovic were to match or best Fed's 17 is that it would set off a never-ending debate about the GOAT. I know the tennis internet loves to debate the topic, but I just have so little interest in it or patience for it. And if we live in a world where most people's minds tell them that Fed is the GOAT, but Djokovic owns the record for major wins with 18 or more and Nadal ran away with the H2H against Fed, we'll never hear the end of it. I say that partially in jest, but I do feel like there's some truth there.