I think it's clear by now that Zoro's main role will be in the main fight against Kaido/Big Mom..... day after day, the Zoro vs King is becoming less and less even reasonable for Oda to do it... NO FREAKING BUILD UP... no tension between them, not even a SINGLE encounter... how shallow is that fight even?
Why don't you guys realize yet that the rooftop is not the final location of the final battle? Holy crap. Use your head. The supernova won't beat Kaidou or Big Mom up there. Xdrake, Hawkins, Yamato, and Apoo will need to be present before the true final battle begins. This again is only the prelude before the finale.
Seriously, Luffy, their strongest combatant, has no haki atm and Kaidou has just gone into his strongest form. What are you guys expecting to happen in this situation.
The strawhat are not coincidentally matched up with the beast pirates while everyone else is doing fodder control or by importance, fighting Big Mom & Kaidou. The beast pirates executives will be taken out by the strawhats. Look at the color spread of the beast pirates. Look at Cp9, baroque works, enel's crew. All of the major organizations are taken down by the strawhats when all of the strawhats are present in the main arc. This is their story!!! Oda will not waste a full battle on characters(not a part of the strawhats or strawhat grandfleet) defeating an executive of the main villain.
It's like you guys haven't figured out Oda's formula by now. It's really common sense.
Luffy vs Kaidou(Eventually)
Zoro vs King(later fights Kaidou when Onigashima reaches the capitol)
Sanji vs Queen(later has some espionage plot with Cp0)
Franky vs Sasaki
Jinbei vs Who's Who
Ulti & Page One vs Nami and Ussop
Robin & Brook vs Black Maria. Brook finds another opponent???
Chopper vs Number 1???
Yamato (new strawhat??) vs Jack?
And despite saying this, you guys are still going to be surprised when Sanji fights Queen, and Zoro fights King.