There are not that many active tour players with 2 or more majors (I am not including Phil) but here is what I see:
Brooks - 5 (2 US Opens, 3 PGA )
Rory - 4 (1 US Open, 1 British, 2 PGA)
Jordan - 3 (1 Masters, 1 US Open, 1 British)
a few with 2 Bubba, ZJ, DJ, Morikawa, JT, Rahm, Scottie
so 10 guys still with a chance (not sure Bubba and ZJ meet that criteria) - and Scottie is, right now, head and shoulders ahead of every one of them. Sure on a given week, someone could put it together, but it is tough to predict that lightning striking; Scottie is winning with his B+ game (tour events, if not majors), so really IMO the only challenge he will have to face is being a parent and how many kids he and Meredith will have. Well that and whomever the next hot shot kid is - right now that torch is Akshay and Aberg, and after that it is someone in their teen.
TLDR - Scottie could have a 3-5 year period of dominance baring injury, parenting or global thermonuclear war