While it is true that not too many Americans have left Emirates in the numbers the company is fearing I say give it time. As I said in a previous post my old company has over 200 Emirates pilots that have applied to join a US major. They only started hiring in Feb so let's just wait and see how many pilots have left Emirates this time next year.
Even if "only" half leave that would be very troubling for Emirates especially when they are having great difficulty recruiting qualified pilots. When you ask around almost everyone agrees that they can not go lower than 2000 flying hours.
So stay tuned.