@Dan:
is
Well, In the green databook (it's just a databook, i know, but Oda was said to be more involved with this one then the others) it says "his ideal crew is over 10 members large!!!". It also says the crew is currently at 9, meaning Luffy is counted, and asks if that means "at least" one more person will join. It's all kind of muddled. Also i think putting a cap on crew size way back at the start of the story, over a decade ago, is kind of weird storytelling, and it probably wasn't meant to be taken literally. So i feel nothing solidly suggests it's going be on more crew member, two more, or even more then that. Any sort of assumption in this situation seems kind of silly to me.
Actually the title is right!
In Chapter 489 the title was - "The Eight" - this is the time when they recruited Brook
In chapter 439 the title was - "The 3rd one and the Seventh one" the 3rd one was Ussop because he rejoin the crew and the seventh one is Franky
In Chapter 6 the title was - "The first Crewmember" - the time Zoro joined
so there is still 9th and 10th member left,
my theory was:
9th member - Fishman/Mermaid
10th member - Giant
And Crocodile is a girl