This is a theory I've been working on for the last couple of days and I think it makes the most of senses.
Remember how in 1056 there was a timelapse between the moment Carrot is appointed Queen and the StrawHats getting ready to sail? I am POSITIVE those days are clue, because then we got the Blackbeard and Boa flashback. My theory is that between those days Carrot somehow was told but an ally or something that that was happening and without anyone noticed went to Amazon Lilly and got advantage of what was happening so she could steal Caterina Devon's fruit so she could disguise herself as Caribou and get into the Sunny.
¿Remember how she can float in the air or practically fly when in Sulong form? ¡She could get to Amazon Lilly in hours without nobody even realizing!
Let's talk seriously Guys
In Vivre card there are 13 places for the strawhat, with Luffy being the 1st and Vivi the last one.
If we assume that Vivi is joining for last and Jimbei is the number 10, we have still 2 spot available. (And it's not about the ships as many assume)
So my guesses are:
1) Yamato joinin later
2) another character/caribou/carrot
gosh people r like u really thought an irrelevant character...yes i did. i liked the c heerfulness she brought to the crew, i was hopeful about chopper doing something so she could do sulong when ever. when luffy used pedro's name to go back into gear 5th i thought...woah she's goin g to truly see the dawn of the world. the lookout role was so cool and would work with their sleep schedules, her friendship with the crew was so cute and i loved how she was as excited about adventure as luffy is. people mock the character and the people who enjoyed her but it's w/e... i never truly thought she would join after wci but i was pumped about the sweet goodbye she'd give to the crew..a last gurchu to luffy, a sweet hug to nami, a salute to her chopbro, and of course another gag where she brought too many carrots and she was going to give the crew some. maybe one last moment talking ab out the dawn of the world or pedro. her telling them she was a queen now... im not sad she didn't joined, im sad oda abandoned her character. in 25 years...she is the only c haracter who sailed with the sh and didn't get an onscreen goodbye...it really stings