Buggy will probably convince Crocodile to go after
John's treasure so they will head to Fullalead then ends up recruiting Gecko Moria and Law. There will be a Mihawk x Perona moment where she believe he went there for her. I also believe that will be the moment where Mihawk will use his full power to level the place down or put Shiryu to his place before departing. Sword will see this as an opportunity to rescue Garb and escape.
As Cross Guild heads towards the Red Line, they will go to Impel Down and Amazon Lily where they're all close to each other. They will free Weevil, offer Doflamingo to join and Hancock has no choice seeing she is now vulnerable. At the Red Line they will encounter Kuma. In other word, all the former warlords will re-unite against one common enemy.