Theory time - It will take five chapters for both Doflamingo and Trebol to be defeated.
Chapter 780: Luffy jumps back up to the top of the plateau. He sees Law, who's barely alive, missing him arm and passed out on the ground. He gets even angrier as Doflamingo gloats. "You're nothing but a raging beast now; I've defeated countless pirates like you in my day. Trebol, go secure Mansherry. By the time you come back, I'll have killed this monkey." Trebol leaves as Luffy and Doffy clash. They're both evenly matched.
Chapter 781: Both start exchanging even blows, but Doffy slowly takes the upper hand. Luffy's rubber powers are a hard match against Doffy's strings. Our hero takes a couple good hits before Doffy decides he doesn't have time to play around with a rookie like Luffy. He launches a powerful attack, seemingly defeating Luffy. Cut to Trebol who suddenly encounters Jesus Burgess!
Chapter 782: Trebol asks what's Burgess doing, and if Blackbeard is interfering in Doffy's affairs. Burgess states that while he's been under the birdcage, he was able to see lots of fights and has seen a lot of interesting powers. Since he couldn't get the Mera Mera no Mi, he's decided to steal one of the executive's powers. He's holding Sugar hostage! Trebol can't let him take her, and attacks. They clash. Jump back to Luffy, who gets up following Doffy's attack and retaliates. He lands a couple good hits. Chapter ends with Doffy finally starting to get angry.
Chapter 783: Doffy's angry and asks Luffy why is he even here; he's got nothing to do with Dressrosa. He was manipulated by Law for revenge and got caught up in other people's business. Luffy doesn't care. He's fighting for his friends. Doffy wonders what happened to Trebol, and gets angrier. Cut back to Trebol vs Burgess. The latter gets the upper hand, and defeats Doffy's last executive. He's about to head up to the roof of the castle before he's stopped by Sabo, who tells him to walk away.
Chapter 784: Burgess laughs and says that he knows he'll have a hard time beating Sabo, having fought him in the colosseum. He congratulates him on winning the fruit, and leaves with Sugar (this fact unbeknownst to Sabo). Cut back to the roof, where Doffy has finally snapped. All of his plans have failed, Dressrosa is lost, his executives defeated, no word on Mansherry, his factory gone. No matter what he does, Luffy keeps getting back up. Cut epic finally and chapter ends with Luffy dealing the finishing blow on the warlord.
...I'm probably 100% wrong, but this is how I'd like to imagine the next couple of chapters play out!