Copy and pasted from my tumblr post:
So, as I predicted a year ago, Bonney will be the 10th member of the Straw Hats. I've held this belief because with no crew left, under the service of no yonkou, she has been alive all this time in the New World. Akainu even let her go. She is obviously a child to someone important enough to have Sanji wanted 'only alive.' I wonder who that person is...
Yes, Bonney is the 35th daughter to Big Mom. After running by herself, with no crew left, she was forced to come to Big Mom's tea party. So, Bonney is now going to be at the tea party, awaiting Sanji. Wanting to be free from her mother's hold again, Bonney will escape with Sanji before the wedding is held. I think it's important we don't just see this panel as a joke. Luffy wants people to join him when his gut tells him they’re the one. Why would he say this girl will join him? He doesn’t even know her! It’s because Luffy’s gut is telling him it’s just destiny.
If it's Bonney, and she escapes with Sanji to seek protection under the Straw Hats. Why wouldn't she then join them? The only dream of hers that we've seen is her desire to get revenge on Blackbeard for what he did at Marineford. How can she do that without joining the group that will sail the entire Grand Line to achieve the One Piece? Blackbeard and his crew is obviously one of the final challenges the Straw Hats will face.
TL;DR: Bonney escapes her mother, Big Mom, who is making her come to her tea party and marry Sanji. To seek protection, she goes with Sanji, and joins the Straw Hats. With them, she can achieve her goal of making the Blackbeard pirates pay for what they did.
Jinbei is making the Sun Pirates again. His crew will join his grand fleet.
Sorry, but no. Jinbe is the tenth member of the crew, as he gilded said, and as Luffy accepted. He's not joining the grand fleet, and he's not remaking the Sun pirates, he's joining the crew. The Sun Pirates may join the fleet, but Jinbe already has a spot on the crew, he only had to take care of some things regarding Big Mom. Lo and behold, this next arc will be involving Big Mom, which means Jinbe will most likely be joining the crew as early as this arc finishing.
Not to mention the fact that Oda already teased Jinbe as the 10th on one of the cover stories where Jinbe was standing next to a kid with a 10 on his shirt.
