I don’t think Luffy should fight DoFlamingo, I prefer Law fight him (well I prefer Sanji vs DoFlamingo but that probably won’t happen. So yea Law).
Right now no one on Punk Hazard is on DoFlamingo’s league. Smoker being a Logia might be able to survive DoFlamingo cut, and Law might be able to counter DoFlamingos cuts with his own, but Luffy has no chance of beating DoFlamingo right now. DoFlamingo is a beast, he’s a Devil Fruit user (possibly) and he’s running over the sea from island to island with no back up, and a grin on his face. I honestly think he’s the strongest Shichibukai. He knows that no one on Punk hazard has a chance against him, he’s confident that he can kill everyone on that island by himself. I don’t think he’ll make it in time to meet the Strawhats, Law, and Smoker though. He’ll probably get there to late and see Monet and Vergo dead and he’ll just blow up the island himself and leave. I don’t think Oda will have DoFlamingo fight so early, because there’s no way someone won’t die.
If DoFlamingo gets there in time this is going to be like Kuma at Thriller Bark, except this time the Strawhats won’t be so lucky.
Finally DoFlamingo is getting involved in the story. I can’t wait to hear about him, his plans, and his Devil Fruit.