So Akainu is fuming while eagerly waiting for Vegapunk's truth bomb. His anger can mean one thing, he's ready to make a decision regarding his loyalty to the World Government depending on what he hears
If in fact the Marines end up defecting, then you can expect Akainu's navy to go against literally everyone
Both the World Government under Gorosei rule and pirates alike will be considered outlaws according to Akainu's absolute justice
His ideal scenario for a just world would be for any corrupt authority or pirate filth to simply cease to exist, Vegapunk is simply giving him the incentive to act on it