Luffys fights almost always run concurrent with the remaining plot threads. This means he usually wins at the absolute end of the arcs conflicts. This MEANS most other conflicts must be resolved before Kaido is defeated.
Just to give a rundown on how other main fights started and ended for Luffy after all other fights finish. Note that the counts below aren't raw content, just how long it takes once the fight "starts" post other fights to its ending:
- Crocodile: Starts in Ch 199 with round 2, round 3 doesn't end till 209. 11 chapters.
- Lucci: Starts Ch 418 (they were fighting before this, just like any other fight, but it truly starts here) and ends Ch 428. 11 chapters
- Doflamingo: "Starts" Ch 779 and ends Ch 790. ~12 chapters. Starting to see a pattern here?
- Katakuri: Starts Ch 879 and ends Ch 896. It's 18 chapters. Note that Luffy really is the only one with a fight this arc.
Now, take this idea and apply it to this arc wirh Kaido. Zoro's fight only ended with 1035, so Luffy vs Kaido technically has only started with 1036 or this chapter, 1037. So, imo, at MINIMUM this will last till 1047/1048. However, Wano is far, FAR larger of an arc than these other ones. There is myriad of plotlines still left unadressed with a ton of characters. And not only that but Big Mom is here and also likely will be defeated.
If I had to guess, I'd say we won't see Kaido/BM down until the mid 1050's or early 1060's, because when you account for the plethora of remaining characters and plotlines that need to end, these Yonko probably won't go down until those are done.