Meh, depends on what else the marines throw at them. I don't think they're just going to mop up everything on the archipelago and be all, "Welp, I'm bored, let's just get going."

It will more likely come down to them running away Blackbeard-style and not dealing with the bulk of the marine force in the first place. Or maybe they'll just accidentally escape from the approaching threat the same way they did when they reached knock-up stream. OR..... the marines might be totally late, see the fake crew lying on the ground unconscious, and think that the strawhats have been defeated, allowing the real crew to easily slip past their detection.