A week has passed since the end of the recent Reverie. Two news leaves the world in awe, with the Shichibukai abolished and a story about Sabo which mentions a death of someone important and an attempted assisanation.
Something has happened to Sabo but let’s be real, he ain’t dead. Many people speculated that he has been captured by Fujitora and/or Green Bull
Garp reveals that something big has happened in Alabasta.
When connecting these facts, it becomes possible, that king Cobra has been assasinated by CP-0 ( he might have known too much) and since both Cobra and Sabo were present at the Reverie and Sabo was (likely) captured, he would have been the perfect scapegoat to blame Cobra’s murder on.
If Sabo is brought to Impel Down, this could be a way for Doflamingo to get out of there too.
We know that Vegapunk has developed something powerful enough to replace the Shichibukai. We will likely see this technology soon, as it would be make perfect sense for the Marines to use it against the now abolished Shichibukai.
At the same time, Blackbeard orders his crew to set sail, stating they are setting out to claim something before the Marines do.
It is implied in this chapter, that this might be the Mera Mera No Mi as Blackbeard has been shown to collect powerful devil fruits.
It is also possible, that Blackbeard is looking for a Road Poneglyph.
Another possibility is, that he is going to attempt to get his hands on an Ancient Weapon (specifically Pluton wich is believed to be in Alabasta).
The secret weapon of the Marines might still be with Vegapunk, so (eventhough it is unlikely), it’s possible that Blackbeard is going to try to get his hands on that.
Blackbeard might also be talking about the Shichibukai and try to recruit them to his crew.
Bonus Theory: The secret weapon of the Marines might be Vegapunk’s recreation of one of the Ancient Weapons.
*Theory by Thistlesmithy