User blog comment:The credo/SHE is Kinemon: The Mulan of One Piece/@comment-972068-20121008062231/@comment-972068-20121008065758

Oda never stated the tenth member would be a girl. Nobody even knows if the crew will have 10 members to begin with (Luffy's guess can be nothing more than a guess). The only thing Oda has announced about the future of One Piece is that he knows exactly how it's going to go. Newer members, places, powers, etc. have yet to be announced in any way. The pirates might not make it to Elbaf. The pirates might not even make it to Raftel. Nobody knows what will happen except Oda himself.

That being said, that doesn't necessarily mean the 10th member won't be a girl, and Monet still has an opportunity to join. She wouldn't be the first villain to join the crew. Not saying she will, I'm just saying there's a possible chance she might. Even if she doesn't, the conclusion that Kinemon is a girl is absolutely ridiculous.