Considering version 1.0 of FFXIV had belts with their own unique appearance, only for that to be scrapped in the changeover to ARR (SE stated this was because having belts with it's own unique appearance actually limited the designs of gear that could be implemented due to clipping issues), it's pretty obvious capes will never be added into this game for the same reason I'm sorry to say.

Really, if SE were going to add capes into this game, they would have done so when ARR was in development.