Legit I think he might be a main villain if Vegapunk has his own arc.
He's tied to Vegapunk and Sentoumaru. Pacifista are based on his powers.
Luffy himself has not technically mastered FS, an ability likely needed to keep up with Kizaru's speed.
But yeah, I wouldn't expect to the fight to be nearly as long as Kaido's or something. Just quick, intense and it's over in a few chapters.
That is, if it happens. Imo, Luffy should beat an Admiral before Zoro and Sanji likely take on the other 2 while he fights Akainu. Again, just a theory.