Last I read was a post from a long time ago stating that new ranks would be added whenever an expansion came out and the level cap raised. Though we haven't seen anything official since said expansion has been announced, I wouldn't be surprised if they were added, but just not talked about. They've kept a lot more under wraps than they've told us, and since this is ultimately something minor compared to what they've announced, I wouldn't be surprised if they just considered it too small to be worth mentioning.....