As strong as the admirals are individually and as strong as the marines are together they play a secondary role to more direct obstacles to luffy’s dreams. Those obstacles being emperors luffy has to face off against to become pirate king and the world government to achieve his secret dream
I say that to say while luffy will more likely than not face off against the 3 og admirals none of them are likely to get a dedicated arc where they are the main big bad for better or worse
He fought kizaru in egghead tho it was barely a fight with neither really fighting to their fullest. Luffy jumping into his g4/5 off the bat in order to mainly speed up the escape process. Something he’d never do in a real fight where time wasn’t an issue. Kizaru mainly focused on everything but luffy half the time. Just trying to get killing vegapunk over with with him being emotionally compromised about it
Kizaru either ending the arc here against Saturn or being saved for later to go all out against a more fitting opponent
Imo Kuzan potentially being an opponent for luffy in elbaf. As for how much a fight it’d end up being idk but it should at least be more than what we got with kizaru. Hopefully luffy finally faces off against a logia awakening. Cause even if kizaru shows it now I very much doubt his fight with luffy is going to continue
Kuzan and luffy will probably end up on decent terms with Kuzan info dumping about Blackbeard, Garp, and other things. Kuzan probably surviving to fight someone else after like Blackbeard or even Koby
With that leaving akainu as the final admiral luffy has to face. Idk exactly where they’ll fight but it’s definitely going to happen to some capacity. Will it be akainu’s final fight idk but it’ll be luffy’s last admiral fight
Imo I think it’ll happen after luffy’s fight with Blackbeard but as for how much time after idk obviously. It could be right after they stop fighting for all we know
Personally for now still think luffy after each emperor luffy will fight one
Basically
Kaido (emperor) -> Borsalino (wg) -> Linlin -> Kuzan -> Teach -> Sakazuki -> Shanks -> Imu