We're at ECMAScript 2017 now. The author is one version behind.
* async functions
* shared buffers (between workers) and atomic operations for these buffers
* additional native object methods (Object.values, Object.entries, Object.getOwnPropertyDescriptor, string padding)
* trailing commas in function argument lists (definition & callsite)
* unicode case folding in /ui
All one can say about it is that it was promoted to Stage 1 18 days ago, that the spec is not currently written, and that it has two dozen issues opened against it.