While Sanji vs Kizaru would be so cool, just 2 guys zooming around at light speed kicking each other’s heads off, I really feel like that’s all there is to it. 2 speedsters fighting. But Sanji’s fights usually involve clashing characters and not just powers.
Sanji’s aversion towards okamas: Sanji vs Mr.2 (Bon Chan is an okama)
Sanji’s code of honor : Sanji vs Jabra (Jabra constantly lying in the middle of the fight)
Sanji’s whole women-invisibility thing: Sanji vs Absalom
And everything related to You-know-who in Wano.
Thus, from what we’ve seen of Kizaru so far, none of what he does actually goes completely against what Sanji stands for.
Ryokugyu on the other hand, he represents something that might relate to Sanji. The guy looks like he might be a pervert, and he hasn’t eaten anything in 3 years, so they’re food and women. Two of Sanji’s most defining characteristics.
Mans gave Fuji food. Is he a chef as well? More parallels.
Another reason for why I think they will fight is that IRL, cattle (cows, BULLS, oxes etc.) suffer from an extremely fatal disease called Black Leg. Hmmm… Black Leg…. doesn’t ring any bells.
So yeah… Black Leg is a disease which is fatal to bulls, which is another reason why I think Black Leg Sanji will fight Green Bull.
So, Sanji shows up to New Marineford, where 1 admiral and 100s, maybe 1000s of fodder remain to hold down the fort (while the rest are away to protect the CD).
Sanji will fight and destroy the Marines present at New Marineford, and on that day Sanji will become the man who the Marines feared the most.