The Linux Graphics Stack
I can understand that Wayland does not want to pay for the complexity of network transparency, but I'd be sorry to see it go entirely.  I'm one of the few people who do make use if X11's network transparency on a regular basis.  Being able to open a web browser on a machine that is several ssh hops away is awfully convenient.  I hope that Wayland has some provisions for reproducing or emulating X11 even if it isn't built into the core.