Considering I dont think the YC's to be mere fodders for top tiers, like some here do, I think Sanji having a legit 1v1 against King, while Zoro and Luffy fight the Yonkos doesn't do anything against the M3 dynamic alone.
But Sanji doesn't have his matchup yet. So....yeah..there's that.
It would simply preserve the Luffy>Zoro>Sanji. I say that because Luffy will, ultimately, be the one to shine the most during the Dome fight. Unfortunately.
But I completely understand Zoro having more significant power displays as we approach the endgame, since Zoro's "main story opponent" is Mihawk. Sanji doesn't have a "main story opponent" like Zoro. It makes little sense to showcase him as much as Zoro.
Oda still maintains the rivalry and their dynamic through other story events, like they being the ones clashing against the enemy's main forces before raid, they both together saving Toko, and so on. The bounty similarity (whether you wanna complain about the reasons for the bounties or whatever). In Oda's mind, these things should be enough to keep their dynamic going, but eventually Zoro will have more significant opponents, due to his goals directly putting him in a rush for power.
I still think the M3 will be the ones tackling the Admirals for the SH's. Jinbei has peaked already and he has shown during Marineford that he can't handle Admiral on his own. I would also consider this to be the case for Sanji, since during FI they were portrayed fighting Wadatsumi together, but Sanji got the RS, which is the justification for his power growth. But there are 4 Admirals. I have HIGH hopes for Yamato, and hopefully she will be the one fighting the 4th Admiral. Not going into detail of who is fighting who. Only Luffy vs Akainu seems set in stone. I've seen the arguments for Zoro vs Fuji, or Zoro vs Kizaru, or Sanji vs Kizaru or Sanji vs Ryokugyu, so I'm putting that on hold. And no, I dont think Kizaru is stronger than Fuji or Ryo just because he is a OG Admiral. I think that's an extremely simplistic view and I'm not fond of that.
(I believe in Sanji vs Roux, but if Mihawk joins Shanks, Sanji vs Beckmann is my new favorite likely fight, beating even Sanji vs King aerial greatness).