Several World of Warcraft community members, including a few of the admins at WoWhead, are reporting that their invites to the Legion beta have arrived. With friends and family, the internal beta begins and, over time, select community members, streamers, ViPs and more will be added before the more extensive beta begins. All in all, it's a good sign.
We'll keep you posted on what comes out of the beta. In the meantime, go check your mailboxes!