Letter from the Producer LIVE Part VIII Q&A Summary (08/23/2013)
http://forum.square-enix.com/ffxiv/threads/64478
The unicorn mount will be added for the official release, and you can obtain it by playing through the conjurer class quest line. Once you obtain it you can ride it as other classes and jobs. Also, depending on the race, female characters will ride the unicorn sidesaddle. We'll be making it possible to obtain various types of mounts moving forward.