Here are some Ethereals and jolly goodness, look at their facial expressions!
Taken from the reddit thread "
(Discussion) Ethereals as playable race - good idea or bad idea?"
The Allied Races system is most likely going to be the go-to introducing new races, rather than create something from the ground as they did with the Draenei/Blood Elves/Pandaren (granted, some of them especially Chen was in Warcraft III) and adding to the roster.
For immersion & monetary gains, Allied Races is a great idea to introduce eventual later races which may or may not be racial variants of the current ones. Highlights the RPG factor which Blizzard is trying to enforce even harder.