Chase Douglas of Canonical has just announced the X Gesture Extension to the X.Org development community and he hopes this will become part of the X Input 2.1 extension. The X Gesture Extension is to work hand-in-hand with the recently-drafted X.Org Multi-Touch Protocol Specification that was written by input-expert Peter Hutterer.
A draft of the X Gesture Extension specification can be found on xorg-devel. The X Gesture Extension provides an interface for X clients to register and receive primitive gesture events and an interface for these clients to act as a gesture engine.
The X Gesture Extension will be found in Ubuntu 10.10, which is using X.Org Server 1.9 but with Canonical's patches. The Multi-Touch and Gesture protocols for X.Org are planned for X Input 2.1, which could come with X.Org Server 1.10 due out early next year.
An introduction to this proposed X extension that's written by Chase Douglas can be found in this mailing list message. At the moment there have been no comments by any of the X.Org developers surrounding this X.Org Gesture Extension.