GNOME 3.14 Still Depends On ConsoleKit, More Systemd Still Planned
For the GNOME 3.14 development cycle was a plan to make most GNOME modules depend on a systemd logind-like API that would only implement the API bits actually used by the respective pieces of GNOME software. The goal was to make this minimal API a shim between the GNOME code and logind for allowing other non-Linux platforms to write an alternative implementation against the API. The purpose of this would be for the BSDs also using GNOME to only have to write a portable implementation of the logind-derived API calls actually being used by GNOME rather than a full, drop-in replacement.
This new logind-like API goal wasn't realized for the GNOME 3.14 cycle and as a result there's still also a requirement on ConsoleKit, but with this non-logind code-path the experience is likely degrading. Going out further, GNOME developers are moving towards systemd user sessions as a replacement to gnome-session.
It looks like gnome-session may still be supported for some time, but the direction is moving towards systemd user sessions. Those wishing to find out more about this work and related topics should check out Olav Vitters' GNOME blog post about systemd in GNOME 3.14 and beyond.