The people who can stop him (Krygios, Zverev, etc.) don't even get far enough in slams to reach him. And he already has a hold on the established players (Cilic, Nishikori, Raonic, del Potro, etc.). Can't say for sure how a match with Thiem would play out.
If Novak does anything good it is studding his opponents and learning from loses.
Ask Tsonga (2:5 -> 16:6), Nishikori (1:2 -> 15:2) and if you like Federer (6:13 -> 24:22), Nadal (4:14 -> 27:25)...
All had positive H2H against Novak at some point in time (and not just positive, but all of them had more then two times more wins then loses!), only for H2H to be turned back into Novak's favor.
Even more examples: Wawrinka (1:2 -> 19:5), Ferrer (2:3 -> 16:5), Verdasco (0:2 -> 11:4), Youzhny (1:2 -> 7:3), Trociki (0:1 -> 13:1)... though these ones can be attributed to loses early in the career.
So, you could bet Novak will do better against Kyrgios, Zverev and Tsitsipas the next time he meets them. It more depends on his motivation to win (and thus to study their game in more depth), then on other factors.