If you've been hoping to play, for instance, a Dark Iron Dwarf, you will be able to IF you own a copy of the World of Warcraft expansion, Battle for Azeroth. The information came through datamined strings of code that indicate the game will make several checks at character creation. This includes whether or not BfA is part of your game client and whether or not you have the Allied Race Unlock achievement for the race you would like to make your character.
While this confirms that BfA will be required for Allied Races, it leaves a number of unanswered questions including:
Could you play Allied Races earlier than Battle for Azeroth release, with a preorder? Similar to Demon Hunters in Legion pre-patch.
Can you earn the Allied Races unlock achievements without Battle for Azeroth purchased?
What are the unlock requirements for each Allied Race?
If you head over to WoWhead, you can also get a look at the race preview interface for each Allied Race in both male and female form with a description of the race as well as a look at the names of the racials each brings in.
Learn more about World of Warcraft: Battle for Azeroth.