"Is wayland replacing the X server?
It could replace X as the native Linux graphics server, but I’m sure X will always be there on the side. I imagine that Wayland and X will coexist in two ways on a Linux desktop: Wayland is a graphics multiplexer for a number of X servers. Linux today typically only uses one X server for GDM and the user session, but we’ll probably see that move to a dedicated GDM X server, an X server for user sessions (spawning more on the fly as more users log in) and maybe a dedicated screensaver/unlock X server. Right now we rely on VT switching to move between X servers, and it’s horrible. We have no control over what the transitions look like and the VT ioctls are pretty bad. Wayland provides a solution here, in that it can host several X servers as they push their root window to Wayland as surfaces. The compositor in this case will be a dedicated session switcher that will cross-fade between X servers or spin them on a cube.
Further down the road we run a user session natively under Wayland with clients written for Wayland. There will still (always) be X applications to run, but we now run these under a root-less X server that is itself a client of the Wayland server. This will inject the X windows into the Wayland session as native looking clients. The session Wayland server can run as a nested Wayland server under the system Wayland server described above, maybe even side by side with X sessions. There’s a number of intermediate steps, such as running the GNOME screen saver as a native wayland client, for example, or running a composited X desktop, where the compositor is a Wayland client, pushing the composited desktop to Wayland. "