Sanji is obviously fighting Queen.
It's funny how that's always been the most obvious match-up and yet people still stumble around it and find new potential opponents for Sanji every other chapter
For Jack i can see this going two ways :
1. Momonosuke and Yamato save the Scabbards and Yamato fights Jack
2. Brook advances to the 4th floor after defeating Black Maria's female subordinates and letting Robin 1 vs 1 her, switches with Jimbe for the Who's Who fight, and then Jimbe fights Jack.
For No.2, Sanji will probably have to get to the Scabbards and save them, and end up fighting Jack for a bit until Jimbe tags in and Sanji's true fight with Queen begins.