I haven't played a lot of Dynasty Warriors games but I do understand the gist of it. From what I remember, that certain characters that weren't controlled within the story could be playable once the story has finished. As of now we have 13 playable characters confirmed. Back at E3 at the Nintendo TreehouseLivestream, Nintendo representatives stated that at least half of the roster will be composed of female characters. Assuming they meant half will be male and half will be female, that means there could be three more male characters that are still yet to be revealed. Only time will tell once the official release for the Japanese version of Hyrule Warriors has arrived and everything has been revealed thanks to the Japanese players.
I still want to believe that Cia has been hinted as a playable character thanks to Nintendo of America's
twitter. If you scroll down to the tweet that starts with Hyrule Warriors features many playable characters from the Zelda universe with a picture of Link, you will see that the above posts actually state the other following characters in pairs: Link and Zelda; Impa and Shiek; Darunia and Ruto; Midna, Agitha and Zant; Fi and Ghirahim;
And Lana and Cia. Do note this was before Ganondorf's reveal. So if these tweets are worth looking over, we have 14 characters confirmed as playable characters for Hyrule Warriors and more information is slowly heading its way.