Luffy will 1v1 Kaido.
Out of all the alliance, Luffy is the only one who has shown the capabilities to hurt kaido. Even if Zoro, Kid, or law gain the ability to hurt him, there are too many bad guys for them to help Luffy.
the whole "kaido is unbeatable in a 1v1" thing was likely set up solely so Luffy can 1v1 kaido.
Also, I don't mean to say that Luffy can 1v1 him right now. At the bare minimum, Luffy would need to awaken his DF in order to beat kaido. However I believe that Luffy will fight a series of 1v1s, similar to how he did in Luffy vs Katakuri and Luffy vs crocodile. He'll probably lose the next rematch, but will get up and take Kaido on for the third time, where he will win.
also, im not saying that other characters like zoro won't take on Kaido, just that they will be more or less insignificant and the only one who will do any real damage to kaido will be Luffy