The three strongest members of the crew will always be Luffy, then Zoro, then Sanji. There is no reason to think that Oda would want to change that, and there’s no reason to think that he will. It’s a dynamic with too much history behind it to be thrown aside. Regardless of how the members in the trio compare to each other- right now Zoro is stronger than Sanji than has ever been before except maybe in East Blue- those three will still be used by Oda as the strongest in the crew, the main fighters, who take on Enemy Number One, Two and Three respectively.
But what Jinbei, and presumably Yamato if she joins, provides is instead of there being a massive gap between the weakest member of the M3 (Sanji) and the strongest member (Franky), there’s two other decently strong members of the crew in between, who are at least comparable to Sanji.
Yes, I’m aware that Jinbei is only fighting WW, but we’ve barely seen a thig from that fight so far. When it’s focused on, I’m still expecting him to be comfortably above Franky, and for WW to cement himself as the strongest F6- which he’s done a good job with portrayal wise already.