Blackbeard would go after Shirahoshi before the world government takes her
Garp was last seen on Fishman island
Blackbeard vs Garp (round 2 of rox vs Garp)
Blackbeard kills garp
Caterina devon disguises herself as Luffy and destroys Fishman island and kills Fishman and the prophecy has been fulfilled
Fishman hate Luffy
Blackbeard captures devon (Luffy)
Fishman calls Blackbeard a hero (similar to how Doflamingo took Dressrossa)
Blackbeard lures Shirahoshi into a trap
Secretly kidnaps her and gets her away from the sea so the sea kings don't interfere.
Luffy finds out Blackbeard killed Garp and kidnapped shirahoshi
Foreshadowing
Imu has Blackbeard and Luffy wanted poster on the ground with Shirashoshi picture stabbed with the sword. This could indicate that Shirahoshi will be the reason for the fight between Blackbeard and Luffy.
Garp was last seen on Fishman island
Blackbeard vs Garp (round 2 of rox vs Garp)
Blackbeard kills garp
Caterina devon disguises herself as Luffy and destroys Fishman island and kills Fishman and the prophecy has been fulfilled
Fishman hate Luffy
Blackbeard captures devon (Luffy)
Fishman calls Blackbeard a hero (similar to how Doflamingo took Dressrossa)
Blackbeard lures Shirahoshi into a trap
Secretly kidnaps her and gets her away from the sea so the sea kings don't interfere.
Luffy finds out Blackbeard killed Garp and kidnapped shirahoshi
Foreshadowing
Imu has Blackbeard and Luffy wanted poster on the ground with Shirashoshi picture stabbed with the sword. This could indicate that Shirahoshi will be the reason for the fight between Blackbeard and Luffy.