There are two characters, who have been heavily linked to becoming the next Straw Hat. These are - Carrot and Yamato.
Like how Oden went on adventures with the Pirate King Roger to Laugh Tale and many more places. Yamato is most likely to be the one who will join the future Pirate King Luffy.
While Franky plays the ukulele in addition of being a shipwright, Luffy's plea was finally fulfilled when Brook joined the crew.
Moreover, with the final saga of the series ongoing in the manga, it is highly unlikely that Oda would want to distract the fans with new crew members instead of focusing on the main storyline. With that in mind, it can be concluded that there won't be new additions to the Straw Hat Pirates.
12th Vivi: If we look at the Native Japanese way to write the number 12, meaning “tō amari futatsu”, we have 2 letters that matches with Nefertari Vivi's name.
The cover page of chapter 861 depicts Nnekomamushi surrounded by 13 cats some with characteristics of the Strawhats. This led to the theory that nekomamushi embody's Thousand Sunny and the 13 cats are the total number of strawhat members by the end of the series.
Usopp remains to be the weakest member of the Straw Hat Pirates. In Wano, the vast majority of the members of the Straw Hat crew received good power-ups. However, Usopp was one of the members who did not receive any power-up and thus is lagging behind.
As strange as it might seem, the most likely candidate to be the next and final Straw Hat is Nefertari Vivi, the princess of Alabasta.
Jinbei agreed, so he didn't really betray anyone with malicious intent, he is more like an itachi level character that had a tough choice to make. So what's the deal with him betraying Luffy. Simple: He is still protecting Fishman Island, his loyalty is to his people, not luffy.
In fact, Yamato openly declared that he would join Luffy on several occasions, however, in the end, he changed his mind. Yamato decided to stay back in Wano simply because Oden started his journey by going from region to region in Wano as well.
Hancock's position within the Kuja Pirates is perhaps the biggest thing preventing her from joining the Straw Hat Pirates, or any other crew for that matter. For one thing, she's nearly irreplaceable as its leader.
Because of threats to the life of his mentor, Zeff, and the other Straw Hat Pirates, Sanji abandons Monkey D. Luffy and his allies to once again assume his position as a prince of Germa Kingdom.
Nico Robin
She stayed with the crew until after the events of the Water Seven arc, when she was found out by the CP-9 and coerced to turn herself in to help the World Government read the Poneglyphs. She initially refused, but agreed to leave after the CP-9 threatened to launch a Buster Call against the Straw Hats.
The protagonists of the One Piece series are all the members of the Straw Hat Pirates (麦わらの一味, Mugiwara no Ichimi), a crew of ten pirates captained by Monkey D. Luffy.
There are seven crews that also represent Luffy
Here's a look at the current fleet in the One Piece series: Orlumbus and the Yonta Maria Grand Fleet (4300 members)
Nami was the crew's third official member, and the Straw Hat navigator first met Luffy and Zoro while she was stealing a treasure map from Buggy the Clown. During this arc, Luffy saves Nami from Buggy, an act which leads to her joining the crew.
She betrayed Luffy and even wished him dead before he formed a crew. Her original membership into the crew was just as an "alliance" with Luffy, which she later ended to return to her home village, but by then, she had become fond of the crew and found it was not so easy to just leave.
7 Luffy Lost His Hat During Marineford
Since he was broken by the death of Ace, Luffy didn't notice that his precious hat had fallen off. The hat would be recovered by its previous owner Shanks, and after a series of hand-offs, it was eventually given to Rayleigh, who finally returned to Luffy as he was recovering.
Crocodile. Crocodile was the president of the secret criminal organization, Baroque Works. He is the longest running primary villain of One Piece as well as the first villain to defeat Luffy. He ate the logia-type devil fruit, the Suna Suna no Mi (Sand Sand fruit).
This character has betrayed the straw hats unexpectedly. Vegapunk is one of the main characters in the Egghead Island arc of One Piece. He is a character full of intrigue that Oda built up carefully from before the timeskip.
But then in fall 2021, One Piece's author, Eiichiro Oda, said in a set of Vivre Cards that Yamato is female. This sent the fanbase into disarray and confusion. Furthermore, after Yamato's face reveal, both the anime and manga re-introduce Yamato as “Kaido's daughter.”
Luffy. There is no doubt that Luffy is the strongest and most powerful Straw Hat Pirate in existence. Luffy has always been considered one of the best fighters in all of One Piece, something that he proved more than once during the Land of Wano arc.
That said, there is one crew member who stands above the rest in terms of loyalty to Luffy: Roronoa Zoro. The Straw Pirates' first mate has proven his loyalty on numerous occasions throughout the series, even putting his crew mates' well-being above his own life.
Well, Chopper is actually the youngest Straw Hat, and he is periodically treated as such. It is not unusual for Chopper to be babied by characters such as Robin and Zoro. His birthday is December 24th, Christmas Eve, which reflects the cold climate he comes from and the fact that he was originally a reindeer.