User blog comment:Kaido King of the Beasts/The Tenth Straw Hat/@comment-24373005-20150116035950

All of the crew has to interact with the new member so we can have an emotional and, in my opinion, boring panel and anime scene where every crew member smiles and agrees with their recruitment.

I really want Viola because she's awesome, and that ability is really strong. But the only ones that she's interacted with are Usopp, Luffy, and Sanji. She isn't going to join. Though the Dressrosa arc is different and I could be completely wrong.

Bartolomeo isn't going to join because that's not his role. He's just an admirer with his own crew who aspires to be like the straw hats, not become one. He's out.

Bellamy isn't really that important. Once Doflamingo is done with he'll appear in the party, the goodbye, and then a cover page or two.

Jinbe seems to be the one that makes the most sense because of his pertinence to the plot. His diversity makes sense for the crew, they all want him to join, he's going to join after Big Mom is beaten, but I don't think he's going to be the tenth. The eleventh, because Luffy said ten members, and that excludes himself.

This is all speculation, and I'm probably wrong, but I put in my two cents.