Keith wrote on the mailing list, "With this, the 1.16 merge window comes to a close. Thanks to everyone who contributed a huge pile of fixes and new features! We're a week behind schedule; Kristian was a bit late with Xwayland, and that included a driver-visible API change that needed fixing (this appears to have been my fault originally)."
The big features introduced during the X.Org Server 1.16 merge window were elminating over one thousand compiler warnings, improvements for Ultra HD 4K monitors, DMX support took a back-seat, and most notably was DRI3 GLAMOR integration. Besides merging the GLAMOR code from being an independent library to now living within the X.Org Server, there were also many GLAMOR performance improvements for this means of doing 2D acceleration generically via OpenGL. Lots of GLAMOR changes were in fact merged for X.Org Server 1.16 as one of the major themes to this release.
Another important feature to X.Org Server 1.16 is support for running the server without root rights in more of the hardware configurations.
Last but certainly not least, the most recent major feature to be merged for X.Org Server 1.16 was initial XWayland support for running legacy X11 games/applications within a Wayland-based environment. The XWayland code merged is using a new XWayland DDX design that takes advantage of GLAMOR for 2D acceleration but is causing problems for NVIDIA's Wayland support plans.
The X.Org Server 1.16 release is expected to happen on 1 July 2014 while on 3 June is when the bug fix window is expected to close.