Board Thread:Speculation House/@comment-25266931-20161221232930/@comment-10380701-20161222013347

If it helps, even if Salem isn't the final boss, it'll always be female. Because according to Monty, the final antagonist is a she.

This may only apply to RWBY (the team) themselves. Once Salem is dealt with and RWBY has done their thing and moved on, and a new ensemble becomes the lead, the antagonist could be something else entirely.