As others have mentioned its not so simple to just add the other genders when as is the headgear can't be displayed on what we will be getting soon, not to mention to make sure the new models wont bug out in cut-scenes.

I know sims modding was mentioned but I also feel like adding FFXI .dat modding as well (As its client side and gives 0 advantage over other players, it was allowed in FFXI) If someone wanted to port a female elvaan outfit to a female hume or mithra the modder would have to re configure the entire outfit so that it fits with the other races skeleton and sometimes it can't be done cause of how complex the differences can get where the game can crash when you change gear in game.

Just wait and see, let them smooth things over first, so the male and female of the new races can be added with minimal to no issue. Plus you know it's not FREE for them to put the character models together.