Whole Cake Island arc is over and Jinbe is officially the ninth member to join the Straw Hat Pirates crew, but I’m pretty sure Carrot will join too soon. Here is why:
She’s a goofy character that goes along with the trio of Chopper, Usopp and Luffy in their funny moments.
She’s strong (if Chopper manages to find a way for her to use Sulong whenever she wants she’s gonna be even stronger).
She’s going to have a bounty after the events of Wano, and like what happened with Franky, the people of Zou will accept her to leave considering that.
She’s a female character and it’s been a long time since the crew got a female character in the mix (I really believe there will be a third woman in the crew before the end of the journey).
She could be the watch on top of the boat (we’ve seen her at this position multiple times already).
She’s a Minks and that add to the fact that the Straw Hat crew is a pretty diverse group.
She has a dream, and it is to see the world.
She has lived a trauma with the rest of the crew with the death of Pedro.
That’s all I can think of right now, but if you take all that into consideration it seems really likely she will join the crew when they come back to Zou, probably after the Wano arc.