It feels like something happened between the bridge scene and the town scene. It already looked like Law was down and Flamingo was killing him back there, yet now Flamingo was pissed off when he was shooting him, as if Law had pulled some last nasty trick out of his hat.

I can't see Flamingo fighting Luffy yet, especially after the phone call to whoever underling he told to handle the colosseum alone. Maybe he will just leave immediately to take care of other stuff. Nevertheless, if Law is down now, Flamingo is free to personally sort things out, including retrieving Caesar. I doubt Flamingo could anymore fight Luffy, Zoro, and the samurai all at once. He ought to be tired as well. The marines arriving right now wouldn't amount to anything against the likes of Zoro and Luffy.