Well, I’m going to be 100% wrong about this, anyway. I might as well make something entertaining.
I predict that during Elbaf, we will see:
-The Revolutionaries make their move on Mariejois, and give us a little breathing room so that the World Government doesn't chase down the Strawhats immediately. Dragon fights Garling while Sabo fights Akainu.
-We get a Dragon flashback during his fight, and a bit of backstory for him.
-Mad Monk Urouge senses Emeth’s Joyboy’s Haki Knot Bomb going off. Urouge starts following the power towards Elbaf, on a pilgrimage to meet his God.
-Shanks’ Haki senses start tingling. Shanks leaves Elbaf to intercept Urouge before he gets to Elbaf. The meeting with Shanks and Luffy will have to wait until a little later.
-Robin reunites with Saul. We all cry manly tears.
-Usopp starts telling the Giants exaggerated tales of his adventures. Everyone believes him and loves him.
-Bonney befriends the Shanks fanboy Giant we saw earlier. It’s revealed that the Littlest Giant is actually a girl.
-Luffy finally learns that his Devil Fruit isn't the Gum-Gum Fruit, but is the Nika Fruit instead.
-Dragon and Sabo win their fights. They start to prepare to take their fight to Pangaea Castle, where Imu is waiting for them.
-After a small fight between Shanks and Urouge, they talk things out and actually start getting along. Shanks and Urouge become drinking buddies. At the same time, Shanks fishes out Law and Bepo out of the ocean. Shanks escorts all of them back to Elbaf under his supervision.
-Robin learns some Nika and/or Void Century lore from the remnants of Ohara's Library and the myths of the Giants.
-We get a tease about a Gateway to the Underworld.
-Luffy meets Prince Loki. Loki turns out to NOT be a villain. Instead, Loki basically mentors Luffy like Yoda. Teaching him how to think more cartoony and free with his powers. This entire time Luffy has been thinking of his powers as "stretching" and now he needs to re-learn how to think of his powers as "creation", instead. As another trickster shapeshifter with ties to snakes, Loki works as a mentor in order to teach Luffy to think more like a Toon.
-The other Strawhats help the Giants fortify their defenses for when the World Government eventually attacks. And they get some training with the Giant Warriors in.
-Smoker arrives at the hospital Koby is at, and we find out what’s in Smoker’s box. Turns out, it’s the same Fast Travel system that Shanks and Blackbeard are using to pop up all over the world faster than you can ever travel over the sea. Some sort of teleportation system. Imu wants Koby to come to Mariejois.
-Imu empowers Koby in a similar way that Imu empowered the Gorosei. Koby gets a new black suit and a powerup. Dark Koby is born!
-As part of his training with his new powers, Dark Koby crushes Dragon and Sabo for Imu. He finishes them off with a dark version of Garp's Galaxy Impact. The Revolution is over.
-The Strawhats learn about The Man Marked By Flames. I don't think they know about him yet.
-Kuzan gets sent by Blackbeard to hunt down The Man Marked By Flames. Kuzan loses, thus hyping up The Man Marked By Flames for when the Strawhats eventually face him.
-Shanks finally returns to the island.
-Luffy and Shanks reunite. Shanks tells Luffy he gets to keep the hat. He's earned it. More manly tears are shed.
-Urouge senses the Nika energy within Luffy, and starts worshiping as his God. This starts of a series of gags. Luffy’s just not having it, and doing some VERY ungodly things that horrify Urouge. Luffy wants to be a God even less than he wants to be a Hero. Gods have to create Meat out of nothing just to give it all away, that's even MORE work than being a hero! Do Gods even get to eat Meat?! Urouge's gags give us a chance to sneak in little nuggets of Nika lore.
-Law tells the Strawhats about his fight with Blackbeard. Law and Bepo are basically along for the ride until the end of the story.
-Usopp and Yasopp awkwardly reunite. They finally break the ice by telling each other tall tales about their adventures. It turns into a battle of who can tell the biggest lie to each other. More manly tears are shed.
-During the reuniting party, we get a little bit of Shanks' backstory.
-After the reuniting party, Shanks tells Luffy that either he needs to join his crew, or he can’t be allowed to leave Elbaf. It’s for the good of the World.
-Interlude to build up dramatic tension: Blackbeard attacks Cross Guild. But, in a twist, Blackbeard offers to HIRE Cross Guild. He offers to PAY Cross Guild to join his side. Buggy immediately agrees for everyone, getting Mihawk and Crocodile even more angry at him. Somehow, Buggy’s crew gets the idea that Buggy got Blackbeard to surrender, making them love him even more, if that was even possible.
-Luffy turns Shanks down flat. We find out why Luffy doesn’t want to be a hero. It’s actually because Shanks saved him back when he was a helpless kid. Luffy knows what it’s like to be on the other side of someone sacrificing themselves to save you. And he HATES the feeling of someone getting hurt because he wasn’t strong enough.
-Shanks and Luffy start to scuffle when…
-Imu and Dark Koby arrive on Elbaf for the finale, using the Fast Travel system to teleport onto the island.
-Shanks and Luffy put their conflict aside for now. Shanks needs to protect his island. And Luffy needs to get his crew out of here.
-Dark Koby defeats Shanks. Shanks lives, but loses his other arm.
-Imu’s “Yokai” form is revealed, but we still don’t see Imu’s human form outside of silhouette. Imu plays the role of Nidhogg and eats/sets fire to the Giant's gigantic tree, thus starting Ragnarok and the Final War.
-Usopp saves the day by distracting Imu with another of his crazy faces. He taught a group of Giants how to make funny faces, and they all make faces at Imu at the same time to distract them at a key moment. This allows them to escape from Imu and go onto the next island. And track down The Man Marked By Flames, which will be the next arc.
-Blackbeard along with Cross Guild collects Vivi from Big News Morgans.
-Big News Morgans is revealed to be Rocks D Xebec, and Blackbeard’s mentor.
-Blackbeard then contacts Imu, saying that he wants to make a trade….
...If any of this actually ends up happening, I'll be surprised. Oda's probably got some surprises in store for us.