Hulk Hogan was the only man in history to hold the IWGP, WWF, and WCW World Heavyweight Championships. Today, the equivalent of that would be holding the IWGP, WWE, and AEW World titles. As of right now, there's only 3 men that could accomplish that great feat….Brock Lesnar, AJ Styles, and Kenny Omega.
Out of those 3 men, who do you think could be the first man to accomplish that someday?
Realistically, there's a better chance of AJ jumping to AEW someday than Brock going to AEW or Omega going to WWE, so I'd say AJ.
But don't forget that it's still possible for Nakamura to pull it off if he gets on a hot streak in WWE and then goes to AEW.