Hooray! A new release of Xorg is always a good reason to celebrate. Long live the all-singing all-dancing feature-rich network-transparent display system which is still the best (and often only) solution for a lot of common user needs, even 39 years after its creation.
Well, Quartz is okay too, even though it lacks network transparency.
Arcan is looking like a very promising successor to the X protocol and Xorg server. It's not there yet, but it gets closer year after year.
I think Linux (and other unix-like system) would be best off with something like rio on plan9. The API should look like a file-system hierarchy, and API virtualization/access management/input output hooks and mapping could also be file-system-like.