Since the end of July has been a call for testing of the new X.Org Server 1.16 packages but still one month later they haven't yet landed the new code. Maarten Lankhorst wrote back then, "now that xorg-server 1.16 has been released with builtin support for glamor acceleration it's time to move all drivers over to it."
The Canonical X PPA offers the "X staging" packages with the new package versions providing the support. Besides the upgraded xserver package there's also version bumps to xserver-xorg-input-evdev, xserver-xorg-video-ati, xserver-xorg-video-intel, and xserver-xorg-video-nouveau that are built against the X.Org Server 1.16 ABI. Those wishing to upgrade to the X.Org Server 1.16 code can run sudo apt-add-repository ppa:canonical-x/x-staging; sudo apt-get update; sudo apt-get dist-upgrade for trying out these packages on Ubuntu 14.10 Utopic. Canonical sadly hasn't done any updates to these packages since the end of July per the Launchpad package details.
Incompatible packages are the NVIDIA 173.xx legacy driver that NVIDIA stopped maintaining (see NVIDIA's Oldest Legacy Driver Will Not Gain New Support) and also the fglrx / Catalyst driver is yet to be compatible with the xorg-server 1.16 ABI.
In terms of the X.Org Server 1.16 Catalyst support, Maarten mentioned back in his call for testing announcement, "will probably not receive updates until near release, so will be temporarily dropped in the archive, use radeon for now." It's really not a surprise and it usually happens that the Catalyst Linux driver is incompatible with the next Ubuntu release due to either Linux kernel or X.Org Server API/ABI breakage until a few weeks or even days before the Ubuntu release. In several cases, AMD has had to send Canonical specialized beta drivers for packaging into the Ubuntu archive in order to offer the proprietary driver support in time.
Let's hope Canonical is finally able to land X.Org Server 1.16 support in Ubuntu 14.10 soon before it's too late.