Its possible that Tsuru and Sengoku pick up Sword and maybe Tashigi and Smoker and go to Cross Guild to save Garp from an execution
I think we're going to get the Underworld (since they're the ones who place and pay out the Cross Guild bounties) live execution of Garp, like Ace, but reversed.
Luffy having to choose between helping Wano and helping Garp in Act 4 would be really interesting, especially after Garp abandoned Ace and chose the WG over him.
Koby saving Garp from execution should be a big part of Act 4. This should also be when Tsuru gets some time to shine: IMO, Tsuru is from Wano, her younger profile is very Wano-esque, to me. Hope Sengoku gets some legit work after he was kinda nerfed due to his position in Marineford.
At the least, I expect Tsuru to have some connection to Wano via Kinemon's wife O-Tsuru, since it's one of the few times in One Piece Oda has doubled up on names, and both are fairly significant characters.
Low-key want to see Tsuru turn Sanji into laundry, too, but that's another discussion.