As it stands right now, no code has been committed to X Server 1.6 since the first release candidate was tagged over two weeks ago. On the X Server 1.6 tracker bug there are still nine open bugs, which means just one bug has been closed since the 5th of January. Hopefully though we will end up seeing a X Server 1.6 release in February.
Among the features that this new X Server update will carry once released are DRI2, RandR 1.3, Predictable Pointer Acceleration, and X Input 1.5 with Device Properties.
X.Org 7.5 / X Server 1.7 was talked about for release in April, but that now looks even more unlikely. Chances are the next X.Org update will not be out until the second half of 2009, unless it receives some significant development help.