Luffy has been foreshadowed to take down Big Mom since the times of FI. He shall be the one to, at least apparently. On Wano? Who knows. But it makes totally sense that he shall be the one to prominently focus on her regardless. Who otherwise exactly?
ZKK can very well occur since it appears that Zoro and Kidd shall be the ones to prominently deal with the monster.
ZKK can very well occur since it appears that Zoro and Kidd shall be the ones to prominently deal with the monster.