He hates pirates, he Is the GA and Luffy Is goint to be PK.
Not to mention:
Unless Akainu goes against the WG, but even if, he has a score to settle
I mean fighting Akainu isn't among Luffy's known objectives so I am wondering why would he stop doing all the things he wants to do and go out of his way to fight a guy that basically just follows orders from higher up... Not to mention that he cant just walk into Marineford and call out Akainu for a 1vs1, things just don't work that way. Surely the Marines want to prevent Luffy from reaching his goal but they would have to seek Luffy out, with a huge mobilized army instead of Luffy seeking them out.
Unless the same scenario as Marineford happens, where Luffy is forced to walk into New Marineford...
Every reason why Luffy would fight Akainu, Sabo has it too and more as the will of Ace lives within him and even talks...
If anyone would need to settle the score it is Ace(Sabo). Surely, Sabo doesn't target Marines but Akainu targets Dragon and since Dragon will have his hands full with higher-ups, Sabo might intervene and protect Dragon's back by keeping Akainu off of him.