I seriously doubt the glamour system is going to completely change anytime soon (6.0 earliest, 7.0 more realistic), for several reasons.

1. There is over 7 years of glamour coding that needs to be rewritten
2. Transmog as of the start of BFA still required you to visit a Transmogrifier to invoke the glamours, however much you liked playing paper doll with the interface.
3. Client vs Server side works differently between WoW and FFXIV
4. PC client and PS4 client changes would be necessary -- WoW has a single interface to be changed
5. People who think that the problem is one of memory, one that can be solved with bitmaps and a little bit of coding, ignore the network issues with additional data, as well as the intricacies of threading through code changes that affect everything you see on screen. Heck, I see enough issues porting into Ul'dah on Balmung, watching players appear in their undergarments for tens of seconds before their gear and glamours arrive.