I guess we'll find out soon but if Robin is the only one there with Sanji to take over the BM fight, then I'm starting to believe more that Brook will fight Who's Who after he reveals himself to Jinbe.
At that point if Robin and Franky are getting 1v1's against 2 of the 3 "mature" Flying 6 members, then I feel like Brook is supposed to fit there alongside them. Plus, Jinbe really shouldn't be too far from Sanji in terms of strength, so I'd expect him to take on a Calamity like Jack/Queen/King with Sanji and potentially Yamato.
Just seems like the possible course of action to have Sanji and Jinbe jump in when Marco is having issues handling the Calamities togetther.
Basically:
1005: Major moments with Robin taking over Sanji's fight, along with Brook joining Jinbe's while WsW reveals himself to Jinbe, maybe he gave him the Scar or something.
1006/1007: Sanji and Jinbe join the fight against Queen and King.
It would probably take longer than this but I can see something like this happening.