User blog comment:Gibbz33/Who do you think is the 7th shichibukai?/@comment-3203286-20140208154200

Ok. First, there's no reason it has to be someone we know.

Second, no he didn't. Go and read that chapter again.

Third, Shanks is a Yonko. He is a direct threat to the World Government. They would not make him a Shichibukai because he would not cooperate.

Fourth, it's clearly Gaimon.