So players "choosing" to play the new race because it's the new thing has almost nothing to do with "player choice"...
I responded just fine to your original post. It's an mmo. Fantasy games are all about fighting a malevolent threat or overcoming impossible odds. Dragons, goblins, ghouls, etc.
How would it make any sense lore-wise if a new race that had never been seen before had a plentiful, massive population in story just so it could reflect the influx of people race changing or rolling the new race on release day? An entire nation of people don't just march up to SW or Org unannounced saying "Hey can we be friends?"
In lore the Draenei are on the run, being pursued by the Burning Legion and at risk of being completely wiped out. The blood elf population is nowhere near as large as it was as a result of Arthas marching upon Quel'thalas and the undead decimating them. But because Blizz decided to make both races playable they should have retconned the lore to say that they are robust in population just to create a correlation between lore numbers and the fact that every other person just happens to roll the new race in an expansion? It's ludicrous. The lore of the Warcraft universe != what players roll and do in game. If that were the case, Onyxia would have officially died when the first level 60 raid downed her, instead of upon the return of Varian. And the hero that saved us from the cataclysm would be some terrible DK named Nomnombabies, or Frostytank instead of Thrall. Blizzard has no responsibility to cater to metagame thinking. Their lore belongs to them. The game itself is just that, a game loosely based off their lore. Canon != individual player action and trends in game.