I honestly have my doubts that we'll get anything beyond Alabasta. Not due to quality and not even really due to ratings. It's just that Netflix likes to cancel shows a little prematurely. And One Piece is probably their most expensive show to make right now. If they want or need to save money...they just end this with Season 3.
But, the live action is fairly popular. So, I could see us possibly going beyond Alabasta. If we go past Alabasta, I feel like we almost HAVE to go until Enies Lobby, at least. Up to Marineford is possible, but less likely. And if they start with the Post-Timeskip seasons, then I feel like Netflix is in this for the long haul. Marineford feels like the absolute limit for what they'd be willing to invest in this show.
Just for the sake of argument, here's how I see any future seasons being structured:
Season 4-Jaya, Skypiea
-Yeah, Jaya leads straight into Skypiea. And, as long as you keep Jaya short, there’s enough for Skypiea to fill out a season.
Season 5-Long Ring Long Land, Water 7,
Season 6-Enies Lobby, Post Enies Lobby
-These two, I’ll admit, I originally had as a single season. And you COULD condense all this into a single season. Water 7 leads directly into Enies Lobby, so there’s a common thought-line there. But, it would be pretty tight. Splitting it up into two seasons almost feels like you’re giving it too much time. But, I’m erring on the side of giving them more time than less. I think ending a seson with Water 7 works because it makes for a really dramatic cliffhanger for the season. Plus, if you’re going to make a set for Water 7, you probably want to spend a lot of time there. I honestly don’t know if LRLL will be that long in the live action version. I could almost see it getting off-screened, as a gag.
Season 7-Thriller Bark, Sabaody, Amazon Lily,
-This would be more of a transition season. There really isn’t a common thought-line through this season to connect all these as a season-long story. It’s just a series of things that happen.
Season 8-Impel Down, Marineford, Post War
-This actually kind of works. You start out with Luffy in jail. He gets free, only to fail. And then we get the hook for the timeskip. There’s a STORY to this season.
Season 9-Return to Sabaody, Fishman Island,
-One leads into the other. It works. The only real question is if Punk Hazard works better here or in the next season. I could see us getting Punk Hazard this season and a cliffhanger of teaming up with Law at the end. But, Fishman Island, despite it’s faults, is a very pretty island. So, I wouldn’t mind spending more time here in live action.
Season 10-Punk Hazard, Dressrosa
-We team up with Law, and then we get to see the payoff to that team up. It works. The only problem is, condensing all of Dressrosa into only 2/3rds of a season might be a little tight. But, I think you can make it work.
Season 11-Zou, Whole Cake
-Zou would kind of just be tacked on. But, again, it’s fine. Again, Whole Cake only gets 2/3rds of a season. But, I think you can make it work.
Season 12-Levely, Wano
-*SIGH* Okay. So, Wano’s actually long enough that you COULD get two seasons out of it. But…I don’t wanna. Just…keep Wano to one season, please. I am not a Wano-fan, so this is just my bias. Maybe even sprinkle in a bit of Levely at the same time, instead of having all happen at the beginning, maybe getting to see a little bit of it in every episode as a B-plot. Just so you can break up Wano a little more. It might be a little tight to cram all of Wano into one season, but it’s basically getting a whole season to itself. So…again, I feel like it could work.
Season 13-Egghead
Season 14-Elbaph
-Actually…I feel like you might be able to combine these two arcs into one season? It depends on how much longer Elbaph is going to be. But, I could see one season that’s half Egghead and half Elbaph. It could work. I’m keeping it as two seasons for now, just because it gives the “Final Saga” more room to breath. This is the “victory lap”, if the live action makes it this far, it’s earned the ability to flesh things out more.
So, if we assume they want to adapt all of One Piece up to the present day, it would take them about 11 seasons after Alabasta. And given it's taking them 2 or 3 years to make a season, that would mean Netflix would have to invest in this show for another 25 years! That's...not going to happen. Netflix does not have the patience for that.
So, I feel like Marineford is probably the ending they're aiming for. But, I think ending it at Enies Lobby is probably more likely. And, frankly, I could see this getting cancelled after Season 3. But, we'll see. Maybe I'm underestimating just how popular the live action series is for Netflix.