As of June 2015: here it is!
http://www.ecma-international.org/ecma-262/6.0
As of June 2014:
The GA will vote on approving it as a Ecma standard at their June 2015 meeting.
At the time of writing (March 2013):
A sixth edition of the standard is currently under development with a target date of December 2013 for completion.
http://ecma-international.org/memento/TC39-M.htm