There's just a weird expectation being set that he needs to die at all from Blackbeard even after meeting Luffy lol. There are a lot of things going on with Shanks that makes it very clear to me he's way more complicated than being yet another death to pile on the Blackbeard hate for Luffy.
- His cleary undefined goals as a pirate. He has a hidden motive as pointed out by Oden, since he cried over something once Roger came back from Laugh Tale after asking him a question. Same motive is pointed out by the fact that he has no idea where Laugh Tale actually is (destroying the gatekeeper theory), plus the fact that he openly talks to genocidal Gorosei about pirates. Also, said "pirate" was kept vague on purpose, so I wouldn't assume it's Blackbeard at all
- The above already entirely points Shanks to being in the "grey" when it comes to being a major faction in this story. If said "pirate" was a threat, you would say that Whitebeard wouldn't go and have conversations with the Gorosei specifically about this. Why didn't Shanks go back to Sengoku, who clearly has his respect? Akainu? Why go to the 5 men who have actively hid a 100 years of history from the world and openly execute populations for knowing its secrets?
- Then there is the pure fact that Luffy wants to fight Shanks, and through all of Shanks' "wild" faces when Luffy is talked about, you can see he wants to do the same. This isnt some friendly Davy back fight forshadowing, this is literally two men willing to beat the shit out of each other for whatever reasons they expect to do so. Luffy thinks Shanks is aiming to become PK, but I think Shanks motive lies WAY deeper than that.
- There is something seriously big behind the mystery of his character. His origins, unclear motive as mentioned before, unwavering belief in Luffy to do something, all while still having a level of personal contradiction (talking to the Gorosei, killing pirates in cold blood, scarring the fuck out of Kid worse than he got it) that shows us that Shanks isn't "all good" as people probably initially thought for the first half of the story.
- Then you just get to the concept of fights and who is likely meant to be fought and when. Take for example Zoro's opponents. Maybe he fights King this arc. Maybe he fights Fuji. Maybe he fights the Monk Gorosei with Shodai. Do you expect any of them to be his final fights? Most importantly, do you expect Shiryu to be his final fight? Most people say no, because after 1000 chapters, we expect Mihawk to be right? Well, consider the fact that Mihawk has now lost his title and does not have autonomy anymore. Consider that the final war is coming and Mihawk probably will be allied with some group or faction. Consider that Mihawk pretty much only has a known association with Shanks. I think its extremely likely he allies with Shanks in the coming war, giving him a place to fight Zoro if Luffy and Shanks collide at the EoS. If you believe these things, it becomes easier to see why Shanks might also be the endgame antagonist.
- Finally, consider Oda's words about knowing the ending to his series since the beginning. Chapter 1 and its two previous versions (Romance Dawn v1 and V2; Chapter 1 is technically Version 3) all involve the Strawhat. Version 1 has Shanks. Version 2 has Luffys Grandfather giving him the hat (not Garp at the time), but this was stated about V2 when published in the compilation book "Wanted!":
"Luffy's grandfather exists simply to keep the readers from discovering Shanks; Oda intended to surprise the viewers with the final story"
Compare this to the fact that Blackbeard has had zero indication of being planned before the series beginning (plus the fact that he wasn't teased until like 140 chapters in, and just not shown until 240 chapters in) Shanks is far, FAR more important to the end than people realize. I would not doubt that he and the strawhat are actually central to the ending of the series and provide full loop in terms of narrative closure. There's actually a ton more here that I could talk about but these are pretty much some of the bigger points.
I entirely believe Blackbeard is not the final antagonist, but simply the penultimate one during the final conflict. Blackbeard, Im, Akainu, or Rocks, whilst all candidates for series ending conflicts with Luffy, I dont believe serve to actually end the series with them.
Shanks provides the emotional depth of the conflict to end the series on. Luffy's secondary goal beyond PK has always been to live up to Shanks' expectations, and I think learning Shanks' true motive (which may be entirely compelling btw) will make the fight between Luffy's role model and him a that much more emotional and worth it. Plus returning the hat or potentially Luffy even dying or even both dying, may provide way more emotional weight on the series ending then him fighting Blackbeard, considering Blackbeards goals have been known for 500+ chapters, nor has Luffy looked up to Blackbeard. Then you just have Zoro fighting Mihawk potentially at this time or Usopp getting full closure with his father.
I just think we are in for a wild ride tbh.
I don't think Shanks makes sense as a final antagonist. It is possible he could serve as an obstacle along the Strawhats way but I don't see any relevance for the Red Hair pirates after Luffy becomes Pirate King.
At this point I think there are only a limited number of ways it could play out:
1) The most popular idea is that the RHP are defeated by the Blackbeard pirates offscreen. If Mihawk allies with the RHPs then that means he goes down to Shiryu too. Conflict between them was set up in Marineford and BB's words indicate an eventual conflict when they are actually ready.
I have some issues with this one though because I believe that Luffy & Shanks have to meet, so all the trolling about Shanks being offscreened aside I don't think it works for the story especially since it would also mean we either won't get to see the RHP in action or if we get to see a fight we would see too much of the BB pirates fighting before facing the Strawhats. It would also mean we won't get a lot of Mihawk if he goes down with the RHPs.
2) The Strawhats meet the RHP shortly after Wano and fight then. It could simply be a friendly bout or it could be a serious showdown where Shanks' secret intentions are revealed.
In this scenario we get to see the RHP pirates in action and resolution for things like Usopp & Yassop and potentially Zoro & Mihawk. It would also mean that the RHPs would be left in a weakened state after the Strawhats win, making it easier for the BB pirates to take them out.
This would mean that Luffy gets to meet Shanks which scenario #1 doesn't allow for. It could also end with Luffy returning the strawhat, BB defeating Shanks and showing up to Raftel with strawhat in hand to deepen the conflict or Shanks telling Luffy to keep the Strawhat but at which point his role in the story would be over, so BB pirates subsequently taking him out would make sense.
It would also allow us to see the RHP in full without revealing the BB pirates fighting secrets until they actually face the Strawhats. That would make the "offscreening" of the RHPs to make sense, giving a logical reason why they lost and after we've already seen what they can do while still keeping the BB Pirates a mystery for the Raftel showdown.
It would also make sense if the final Red Poneglyph was tied to the Red Hair pirates so 3 Yonkou besides the final one would be out of the picture before the battle for the Pirate King.
The major issue I have with this one is Zoro becoming WSS before facing Shiryu.
3) The Strawhats don't encounter the RHP until after Luffy becomes Pirate King and the BB pirates have likely been defeated. This one doesn't make much sense because there's no use for a Yonkou after someone is already Pirate King. There wouldn't be any bigger stakes for the Pirate King's crew to face a mere Yonkou crew. If Mihawk allied with them then it would also mean Luffy achieved his goal before Zoro which kills any hype for that.
4) The RHPs somehow take over the World Government and become the antagonists of the Final War. This has similar problems to the prior one. Unless some serious shenanigans along the lines of theories that Shanks is secretly a Celestial (something already done with Doflamingo) and the heir to the throne or such, it wouldn't make sense for him to be present in that conflict. There's no reason for the WG's forces to bow to pirates. There's no sense in the Strawhats' final battles being carbon copies of the one they would have already had to become the Pirate King crew. There's no reason for Mihawk to be a party to such a plan either. Shanks' prior actions wouldn't make sense in that context either.
5) The Strawhats face the RHPs after the final war with the WG. At this point there's simply no gravitas to it. Any conflict after the greatest war in the world would be empty and lackluster. It would mean that Zoro becomes the WSS as basically an afterthought and there's no point for a Yonkou to still be present after the Yonkou saga and resolution of all the major secrets of the story. This is the option that makes the least sense to me.
Regardless of what option it ends up being I believe several things have to occur in the narrative:
- Luffy & Shanks have to meet
- The RHP & BB pirates should have a showdown
- Zoro should become WSS before or at Raftel
- No Yonkou should remain after Luffy becomes Pirate King.
- The final antagonist must seat on the Empty Throne. The King of the World, whether the position is usurped or not must be the last to go down.