LLamaBoy

It's not possible that the new race can be the Broken - they're a corrupted splinter group of Draenei that serve under Illidan, who controls them with demonic magics. If it's Draenei, it'll likely be another faction living elsewhere in Outland.

Also Eredar are very unlikely, as they're described in lore as a race of immensly powerful, extremely evil demons. Something the Alliance would never even consider siding with.

The above is my opinion, based on the facts stated in Warraft's lore.