If Marco ends up full-on fighting King, it would be very illogical of him to tell Zoro that this war is for the new generation. Defeating King would mean the same thing as he's a part of the same war. Oda spoit Marco's cool line there if the 1v1 happens. And no, I'm not saying this because I want Sanji vs King. I already said that King should be too strong for Sanji and that it's too early for him to become a YC1+ character.
I don't know who King should end up fighting but if it's Marco, that would be pretty contradictory going by what Marco said.