I'm still waiting for them to follow up on a claim at a lore panel that there were more clans of Au Ra then the Raen and Xaela.

Perhaps it's overseas in Meracydia and/or the New World that they dwell, and maybe they and other clans unique to those lands might become available as customization in lieu of adding more races beyond the ones we have already. A lot of people have lamented that female Au Ra aren't more similar to the males in stature and build, so maybe that could eventually be a thing in such manner.