Well, with their abundance of cash and highly discounted unit price, due to bulk ordering, Emirates can buy as many of any type that they like and then go into the leasing business, they don't have to, nor would they want to, fly them all themselves, I think.
They could certainly corner the market in leasing to other Middle Eastern and Muslim country airlines as well as offer very competative rates to anyone else that was interested! The Emirates order book may, in fact, represent the wish list of several airlines, not just EK.
Just my thoughts.