I always thought it would be cool if we could have a Subrace unlockable when you have a character of that race reach level 30.
In that case one you've played a NE for a while you could unlock the ability to create a High elve character.
I doubt that Blizz will, purely because if they had a new expac and horde got a completely new race and Alliance just got a race horde has had for yeeears there will probably be a bit of an outcry, though now that Blizz are making all new race models I guess they could try and do something to make the two a little more visually distinct.
Since all the server transfer and faction changing became easily available I think "Faction balance" became a non-issue. I expect there are VERY few servers that are anywhere near being balanced between Horde and Ali now.