Kristian Høgsberg wrote on the wayland-devel list, "Wayland 1.0 is just around the corner and we have a couple of blockers for that release: thread safety of the client side API and the surface commit feature. Pekka has been working on the commit part and these eight patches rework the client library to be thread safe. I've been meaning to release 1.0 this week, but we may have to take a few more days to let these changes settle down. We ended up changing the API and protocol a little more and a little closer to 1.0 than I was hoping we'd need to."
With the patches Kristian posted as part of the list, Wayland is now thread-safe just in time for the 1.0 release. Since last month we have known the Wayland 1.0 stable release was imminent while since the beginning of this year Kristian was hoping for an H1'2012 release.
Kristian has said several times now that Wayland 1.0 will not mark the end of X.Org and the domination of Wayland but simply it's a point at which Wayland developers will maintain backwards compatibility and officially support Wayland and the reference Weston compositor. It will be some time and several releases before Wayland is effectively feature-complete and ready to take on the Linux desktop world.
With these last minute API and protocol changes just days ahead of the Wayland 1.0 release, all Wayland clients now need to be updated. As Høgsberg wrote in his message, "With these and Pekkas changes, we'll have to update the clients once more. Unfortunately Mesa 9.0 was just released, so we'll have to get these changes into a 9.0.1 release. Toolkits will need a change as well."