X Input 2.1 Not Coming Until X.Org Server 1.12
X Input 2.1 was originally talked about for X.Org Server 1.10 with its initial multi-touch implementation having been published back in late 2010.
After this version of the X Input extension missed the 1.10 cycle, it was getting back on track for a xorg-server 1.11 merge. The multi-touch work has already went through several revisions by Daniel Stone and Canonical.
This work was looking like it would finally land for X.Org Server 1.11 when it's released in August, but it doesn't look like it will make the merge window closing.