Yeah as said in another thread the top 4 seems about as clear cut and stable as it has been in ages really, the SFs of the YEC clearly include the best 4 players in the world. Rune and Z can get close to that but both had various injury issues this year and will be looking to improve. The key for them is their unimpressive forehands, if they could improve them to the top level consistently they could be legitimate Slam contenders.
But yeah things do feel rather stable going into next year. I think that aside from some sort of nuclear leap from Fils Shelton or Ruud (yes, really, haven’t fully written him off) we won’t see any new Top 5 members and should have the same general 12 guys in contention for YEC.
Nadal is actually the wild card to get back to the top 5 moreso than any young player breaking out. Shelton will be interesting though.