In the real airline industry the airlines are able to order 737MAX, A320NEO, C-series, and A350 before they are put into production and get a very hefty discount. This should be implemented into airline sim so that the airlines who are established can buy airplanes that arent yet released and get first delivery.
AS is based on real data...they usually release new airplanes a few months AFTER the real airplane is first delivered. I see this as a good thing because the performance we get will be realistic. If we get 737MAX or A320neo now...what would be their performance? The AS team can't just create something out of nowhere right...and certainly can't guess on the claims of "20% fuel reduction" that kinda thing.
On the other hand, since you've mentioned, I would like to see the A320 sharklets... :)