See harmony for requirements, goals, and means informing and guiding the proposals under development for ES-Harmony.
Lacking a formal language specification, the following list is not definitive, but it should reflect consensus achieved so far in TC39. Anything can be revisited for a good reason, of course.
The following list will grow, but not without bound before the next ECMA-262 Edition is constructed. Without prematurely triaging or using “ES6” (which might have to be used for a short-term edition, worst-case), for now let’s focus on near-term proposals while keeping important longer-term strawman proposals warm.
— Brendan Eich 2009/07/29 23:51
Most of the proposal on this page have already been incorporated into the ECMAScript 6 specification drafts. In general, once a proposal is incorporated into the draft specification, the latest draft takes precedence over the proposal. However, at any point in time, the integration of some proposal may still be incomplete and both proposal and the specification drafts may contain errors. If in doubt about the status of any proposal or the draft specification, post a question to es-discuss. Remember, everything is subject to change up until the point that the final draft is approved by the Ecma General Assembly.
— Allen Wirfs-Brock 2013/01/19 19:56
TC39 Process that applies for the features from ES7 forward is described here:TC39 Process
— Dmitry Lomov 2014/01/30 11:47
...prefix operator for expanding an array actual parameter into its elements (allen)
inconstructs, and proxy enumeration that scales (brendan, dherman)