In the official blog post for Patch 10.1.5, Fractures in Time, Blizzard has confirmed that all races will be available to the Warlock class! In addition to this, pet customization for Warlocks is also coming in Patch 10.1.5, with an all-new questline leading to a new appearance to your Imp, and the option to customize all your pets in the barbershop!
The Warlock Class Expands to New Races In the Fractures in Time content update, the Warlock class will become available to Night Elves, Draenei, Lightforged Draenei, Pandaren, Kul Tiran, Tauren, Highmountain Tauren, Mag’har Orcs, and Zandalari Trolls. Warlocks will also be able to undertake a new quest line starting with the quest «Beginning Impositions,” which will unlock a new imp pet customization. Read more on wowhead.com