Canonical Has Yet To Land X.Org Server 1.16 For Ubuntu 14.10
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.