Back in December Stephen Chandler Paul published this protocol as a similar specification to X11's primary selection clipboard. This Red Hat developer has been doing this since they are trying to fill in the gaps for where Wayland doesn't yet have functionality to match what's currently provided by the X.Org Server.
Those unfamiliar with the primary selection can see this GNOME Wiki page. The original RFC patches for the protocol work can be found here and there's also a basic implementation for Wayland's Weston reference compositor. Through today, this work continues to be discussed among upstream developers.
Let's hope all this work and the other remaining Wayland TODO items will get cleared up soon so that Fedora 24 in May will be the first tier-one Linux distribution defaulting to Wayland rather than an X.Org Server.