@Deicide:
It's a small bet of mine. I feel the cover story is being drawn out for its events to lead to tie in with the main story.
Also, having the Firetanks fight Big Mom again would make the events of WCI to come back full circle (which is why I also think the SHs from that arc, Sanji, Jinbe, Nami, Chopper and Brook, would be there to fight BM again). Also, I think it's unexpected allies, like the Firetanks or Moria, that will allow the Alliance a chance to fight back, as I believe Kaido is aware of the current invasion.
I think the other Big Mom children will climb the waterfall again and arrive during Act 4. The missing ones (like Karakuri) are mostly the ones that were already fought and defeated in WCI (thought Oven's absence is strange, as he was a major opponent who didn't get defeated then).
I think this arc is the end of Kaido and Big Mom. The next saga, IMO, will deal with CP0/Revolutionaries and the SSG/Vegapunk, while in the background Blackbeard moves against Shanks, thus setting up the big final fights between the Blackbeard, Luffy and the Marines for the last saga.
It's possible. I don't really think the Linlin story is going to wrap here though. I do agree the next arc will be Vegapunk / SSG and Revolutionary focused.
I guess, I think that Wano is the end of Linlin's role as an antagonist, but that she will continue to play a role in the story into Elbaf.
If you consider Punk Hazard through Wano to be the Big Mom / Kaido saga, I feel like the next saga will focus on Shanks and Teach, leading up to Laugh Tale. I think Luffy vs. Teach is the last battle of the New World before the discovery of One Piece. Then the last saga is the Great War, Void Century, Im, World Government.
I do agree that big events are going to happen with Shanks and Teach in the next saga, but I think the real endgame can really only come into focus after One Piece is discovered.
This is obviously baseless speculation, but before Laugh Tale, I think we still need to get an Elbaf arc and a Vegapunk / SSG arc. I suspect we will have at least one arc in which Uranus plays a major role in the story. We have had arcs focused on Pluton and Poseidon. I suspect that arc could be Elbaf. I really don't think there is a Road Poneglyph on Elbaf at this point. The missing Road Poneglyph was moved from Fishman Island sometime in the past 24 years, so it's not the original location that is a mystery, but who moved it, where they moved it to, and for what reason. It happened sometime before Linlin took over Fishman Island, else she'd likely have had two Road Poneglyphs. I wonder if we'll get some hints about Uranus during this arc given Linlin and Kaido's stated ambition.