Now that Luffy was one-shotted by Kaidou, I believe he will realize that in his current state he has no chance of beating of Kaidou. So Luffy needs a power up and some kind of confidence boost, this is why I believe Luffy will need to leave Wano for that.
-YOUTUBE VERSION OF THE THEORY-
Now to start with, I don’t think Luffy will be captured by Kaidou. I think Luffy will escape Kaidou either with Law or Shutenmaru’s help. The best way I think this will be possible is Law using Room to switch places with Luffy once he is being taken in by Kaidou’s underlings. This is where Luffy’s sword comes in handy. Since Luffy is wearing a sword, Law can switch places with his sword. Thereby he will be having his weapon with him in prison.
I feel that after Luffy wakes up, he will see that Tama is in really bad health and Chopper does not have the skill within him to heal her. Seeing her in that state will make Luffy realise that all this was his fault and he needs to do something to save her.
I think here is where Inuarashi will tell Luffy that Tama can be saved if he takes her to MARCO the Phoenix. I believe Marco will be able to heal Tama with his “Flames of Rebirth”.
Also, note that the cat which he heals is also named Tama. Could this be a foreshadowing that he will heal her?
Going to Marco will serve quite a few purposes:
1- Tama will get healed. The first one is obvious because that is the main reason for the visit.
2- Luffy will see Ace’s grave. Since Marco is in the same Island Ace and Whitebeard are buried, it stands within reason that Luffy will go to see Ace’s grave. I believe that seeing Ace’s grave will strengthen his resolve to pursue his dream. Just like it did for Sabo.
3- Luffy will fulfill Ace’s promise to Tama. Since Luffy has taken Tama to another Island, he will partly fulfill Ace’s promise to her.
4- Luffy will get a power-up. I believe once there Luffy will find someone who I think will teach him how to awaken his Devil Fruit. It could be someone from Whitebeard Pirates, maybe Marco himself, or a former Roger Pirate like Scopper Gaban.
5- Chopper’s dream. I believe seeing Marco curing Tama, will give Chopper a clue about his dream to make his miracle cure for all diseases.
6- Edward Weevil. One of the most important things about this arc is Luffy’s encounter with the final Shichibukai. I think Weevil will somehow find out about where Marco is by someone following Luffy in his journey to Marco. In any case, I think he will arrive there after Luffy learns the theory in awakening his Devil Fruit.
Weevil will then obliterate everyone around and since Marco is healing Tama, I think he cannot take part in the battle. So it will be up to Luffy to stop him. In this fight, I think Luffy will learn how to use awakening or any other power up.
7- New Allies to war. After this battle, I think Weevil will become a friend of Luffy. And might even help in the battle against Kaidou. Because personally, Weevil does not seem to be bad. It’s only because of his mother that he was killing the former Whitebeard allies.
Also since Luffy beats Weevil and saves the people of the Island, Marco might also join the crew.
Further, Luffy could meet Gekko Moriah here. He could have been the one who might have tipped Weevil about Luffy being here. And in the distraction, he would try to steal Ace and Whitebeard’s bodies. But ultimately with his plans in ruin and seeing how Luffy is prepared to fight Kaidou, he might join the alliance as well.
Anyway, this could be in a way Luffy making a lot of allies. Since Luffy will have 2 weeks time, I think will be the best way Luffy can get stronger and get a few allies to his war against Kaidou. Also since it is Law who gets captured, he could secretly convince Kidd to join his alliance in the prison.
*Theory by Ashura The Demon