Exactly, and the last time they did this they had around 6-7k playerbase, wich has trippled since.
Warmane is expanding with a huge amount and more players want to join but are then turned off by the queue or the x1 experience rate alternative.
Opening a second realm, (now when cross realm also will be implemented) really has no downside.
I have no doubt that a second realm would fill up really fast aswell.