I think King and Queen are going to be fought by a duo: The two of them were introduced together, they both fought Big Mom, they have appeared together throughout the entire raid and both are currently fighting Marco. This duo is probably going to include Sanji, whether his primary opponent is King or Queen is up for debate.
1. Sanji and Marco. I don't think Marco will take out a big name this arc, unless he fights Perospero. He talked about how the New Generation is important. I think he's going to be defeated in a couple of chapters. I suppose his primary fight would be King.
2. Sanji and Drake. Drake has established beef with Queen and is currently defending Chopper, who Queen wants to kill. Sanji clashed with King earlier in the raid.
3. Sanji and Chopper. This one is unlikely. Chopper would die in seconds.
4. Sanji and Yamato. Yamato has been protecting Momo the entire raid. King said that if Momo dies, the raid is over. Queen knows Sanji's father and is also a cyborg. Yamato will probably fight Jack and then go the roof.
5. Sanji and Jinbe. My personal favorite, Sanji would take on the fast, fire using flier while Jinbe fights the slower beefier fighter.
6. Sanji and Zoro. This one is pretty obvious. Swordsman vs Zoro, Weirdo vs Sanji. I don't think this one is likely. Zoro belongs on the roof.