I mean if we look at where the story is, the straw hats have had all but one of the keys to laugh tale for a while, and if it’s their sole goal it can’t take too long to find. Stuff has escalated a lot since wano and luffy becoming an emperor, we saw shanks comment directly on meeting luffy and implied he’s close to the strength he needs but not quite there so it’ll probably be just one serious jump in power until he’s worthy of being pirate king.
If there are two pairs who will meet, it makes sense for it to be shanks + luffy and the sopp father-son duo. Luffy might be strong enough after elbaf, and if shanks is going for the one piece it’s a signal that Luffy will have to go for it soon (so he isn’t beaten). The guy loves to tease Luffy, hazing him before he gets the one piece will probably be his last tease.
But it could also, because of the vagaries, refer to pairs like weevil and Marco, or Loki and mosa. Or Blackbeard and Imu. Who knows, he’s introduced so many possible threads. We know vivi is sending messages to the straw hats, so it may be a 2 year long detour.