Caesar will do what robin did in alabasta. He will be in sunny ship before they reach Wano. Caesar is a totally evil shit i know they hate him. But luffy's always been thinking of caesar in zou arc calling him gas guy and he thinks hes funny. Caesar is definitely a funny guy. Strawhats hate him but they definitely saw his good side and useful side in zou arc. Caesar will feel responsible for giving Kaidou his poison chemicals. He will want to take it back even if i takes fighting his fear of kaidou. Caesar will be ultra useful in Wano war since hes the only one capable of removing the poison gas that kaidou might use. It will be a huge help. And after this war, Caesar will finally be a strawhat and will serve as the team's scientist. He can definitely improve the sunny ship with his chemicals, help improvise weapons of usopp franky and nami, help luffy increase his immunity from poison, and he definitely has a dream: to surpass vegapunk as the greatest scientist.