WARNING: The following contains spoilers for One Piece Chapter 1031, "Warrior of Science," by Eiichiro Oda, Stephen Paul, and Vanessa Satone, available in English from Viz Media.
In One Piece's most recent chapter, series creator Eiichiro Oda seems to be setting up the death of at least one of the Straw Hats. Throughout the series' long history, death has somewhat always been avoided unless it was part of a character's flashback or origin story. It can even be argued that Ace and Whitebeard's death at the end of Marineford was just the final part of Luffy's origin story.
While most deaths in the story of One Piece have either been fake-outs or for character development, Oda has only rarely put the Straw Hats in positions where they might actually die. Now though, things might be quite different. The Wano arc has been set up and hyped since Punk Hazard -- or Fishman Island if you take Big Mom's involvement into account. As such, the stakes of the story need to reflect that and it seems that readers are finally able to see just how high they are. Unfortunately for readers, while one Straw Hat, in particular, has had their death somewhat foreshadowed, in reality, there are actually multiple contenders for this unfortunate fate.
Starting with Sanji, it seems like he is the character whose death has been the most foreshadowed. For the last few chapters, it's been clear that Sanji's body is changing and becoming much more like that of his brothers and sisters. There are many reasons why these changes don't sit right with him, but the main one is that he is terrified of becoming a merciless monster like his brothers are.
One of Sanji's core character traits is his chivalry and kindness. His chivalry in particular has been highlighted multiple times throughout the Raid on Onigashima, with his capture by Black Maria highlighting it. Sanji can't hit women, plain and simple. It's been stated in the past by both in-story characters and Oda himself that it's not something he won't do, but literally CANNOT do, most likely due to his upbringing and just personality.
This has caused multiple problems in the story and has even been a point of contention among the fanbase for decades. However, in the most recent chapter, it seems that Sanji may have struck a woman and an innocent one at that. What exactly transpired isn't actually clear, though it has left Sanji in a state of panic at the thought of losing himself to his father's enhancements. It's made worse when he realizes that what he might become could be more beneficial to his crew, even if it costs him his soul.
In something of a desperate plea, Sanji swallows his pride and requests that Zoro kill him if the worst happens and he is no longer himself by the time the raid is over. This is a huge moment of character development and depth, but it's hard to imagine that this wasn't meant to foreshadow some future event. Not to say that said event is the death of everyone's favorite pirate cook, but with nothing else to go on it's very hard to deny the possibility that the Wano arc ends on a much more somber note than previously thought.
Never one to be outdone by Sanji, Zoro himself is in an interesting predicament himself. Currently fighting Kaido's right-hand-man, King the Wildfire, Zoro has his work cut out for him. Unlike Sanji who has received multiple new powers this arc, Zoro technically shouldn't even be fighting at all at this point (what else is new). It was revealed earlier that he was a user of Conqueror's Haki as well as its advanced form, although Zoro hasn't been able to use it over and over again like Luffy has been able to. While this could just be a result of the damage he took and the energy he spent fighting Kaido and Big Mom with the other Supernovas, he was pretty much incapacitated after using his Ashura technique.
The only reason Zoro is still able to even stand is because of the Minks and their miracle drug. However, while it brought him back to full strength, it was warned that afterward Zoro's injuries and pain would be much greater than they were before, making this a double-edged sword. To top it off, Zoro has been having a much harder time dealing with King than Sanji has with Queen, with King's ability to fly as well as incredibly versatile fighting style being very hard for Zoro to counter.
With all that said, it is unlikely that Zoro will die here. Not only would it be a poor decision narratively, it practically wouldn't make any sense. With his entire character arc being solely about becoming the World's Greatest Swordsman and beating Mihawk in a rematch, Zoro's death on Wano would feel quite premature, especially with the relatively recent revelation of his Conqueror's Haki.
Now, this one, in particular, might seem a bit out of the left-field, but there is a surprising amount of evidence to back up this possibility. Currently, Brook is escorting Nico Robin back to the rest of the Straw Hats. However, in hot pursuit are the CP-0 agents that have been hiding out on the island throughout the entirety of the raid. The other Straw Hats' heavy hitters are either preoccupied or nowhere to be seen, including Robin herself, which means Brook is most likely going to have to defend her on his own.
This would actually make sense, because aside from Usopp, Brook is the only Straw Hat that hasn't gotten their one-on-one fight this arc. Much like Usopp actually, Brook acted as support for one of their crew's Femme Fatales. Unfortunately, CP-0 agents might be even stronger than Kaido's Tobi Roppo, as they are described by Robin to be in a league of their own.
As strong as Brook is, even if he could beat one of the agents, it's unlikely that he could beat both of them. And while they have been ordered to capture Robin alive, there is no such order for Brook. His death might not be guaranteed or even foreshadowed the way Sanji's was, it's hard to ignore the possibility. However, due to his somewhat undead nature, killing him might be much harder than it sounds.
All-in-all, this raid has shaped up to be an exciting story. With so much going on that it's hard to keep track of all the moving pieces, it has also created an atmosphere of unknown possibility. As of now, it might not be clear what Oda intends to do with his characters, but it's clear that readers need to start preparing for the worst just in case.