Lennart Poettering has published patches this Sunday to provide support for udev/systemd multi-seat input device hot-plugging support for the X.Org Server.
Details about the multi-seat systemd implementation can be found in this FreeDesktop.org specification
. Adding in this support to the X.Org Server presents a new "-seat" X Server switch.
Those wishing to learn about this new X.Org Server multi-seat support can see this mailing list message