I think they will be in 7.3.5, but maybe not at patch release. Why?
- Test Realm Content and UI.
- All these four races is Legion-binded and the part of current expanion story and we should treat their story joining to Ally/Horde as the epilogue of the history.
- Now we have to wait about a year during new content release. It would be good for Blizzard to share a small part of the expanion earlier, especially if this feature looks complete or almost complete even now. What's the point of keeping ther to the really start of BfA, when you can use them to keep many players subscription up?
- Most gameplay that Allied Races provide uses current content. It's cheap to develop and may make player stay with Legion a bit longer, I mean those who want to jump into next expanion with a new character as any of Allied Race, and I think there will be many.