Wirfs-Brock preaches Harmony
When it comes down to actual features in Harmony, these will include: sandboxes and module loaders, array comprehensions, binary data objects, built-in hash maps and sets, and super-method calls. Some of these, such as block scoping, array comprehension, maps and proxy, have already made it into browsers, specifically Firefox and Chrome between 2006 and 2008. Elsewhere "some of these details aren't really pinned down yet," Wirfs-Brock says.
In the meantime, there's no date for Harmony, although you can expect to be using Harmony's features in five to six years from now. Ahead of that, ECMAScript 6 is expected to be formalised by the end of 2013 when Wirfs-Brock also expects most browsers will be running ECMAScript 5.
Meanwhile, Google marches on with Dart.