If that is the case glad I got my MBA 13" when I did.. the battery life on that thing is incredible and no matter what Apple does, adding a battery hogging retina display will no doubt reduce it significantly, this is the reason that I decided against a macbook pro.
Battery life will be same or less by 1-2 hours at most. Even if you didn't get your MBA at this time the (eventually) old model (the one you have) will still be available or purchase for a while.