Accellera have released UVM1.2 (June 24 2014).
Here in the Verification Academy Cookbook we have a summary of the UVM1.2 changes that affect back-compatibility in the various Cookbook topics. You can find this here and all the affected Cookbook pages have a notice at the top to warn you of differences between UVM-1.1x and UVM-1.2x in that topic area.
You can also browse the UVM1.2 class reference documentation
Although many features of UVM1.2 are not back-compatible (and so using those features will require you to change your testbench code) the good news is that if you follow our guidelines here in the UVM Cookbook, you will not experience too much pain when you migrate to UVM1.2 at some future date.
Please give us feedback on UVM1.2 - we would especially like to hear which features you plan to make use of in your testbenches or VIP.