This is probably a stupid question but why can't someone make an X11 version that speeds up and optimizes everything but breaks backwards compatibility?
That's basically Wayland. If we're lucky, the KMS+Wayland+XWayland stack will end up with a better architecture, backwards compatibility, and less code than the old XOrg.
(My hope is inspired by ZFS which, due to its "rampant layering violations", had more features and less code than the UFS+LVM stack it replaced.)
There's really no point to doing that, since X is a protocol, and a pretty flexible one at that. Your new shiny can have an X server running in it to act as a go-between and talk something more modern with the new stuff instead.
The OP would have been able to do the same stuff with Exceed on Windows or the X server that comes with OSX, after all. X11's survival on linux seems to be largely a matter of momentum and the fact that it's the least common denominator in a fragmented landscape.
But now Ubuntu has approached the level of ubiquitousness that's necessary to push for a real change (thus mir) and the rest of the linux world is rallying behind wayland.
What are you going to run on it? 99% of userland programs expect compatibility with some historical version of X11. Are you going to rewrite GNOME and KDE and everything else?
Many userland applications don't use X libraries directly, but use a toolkit like Qt and GTK. Both projects are working on Wayland support [1, 2], bypassing X completely.
