Things should be clearer now that the "Stage Process" [1] is more transparent. Object.observe made it only as far as Stage 2 ("Draft"), but async/await has already pushed on to Stage 3 ("Candidate"), making it much more likely it will hit Stage 4 ("Final") just as soon as a plurality of web browsers support it. (...and as soon as it hits Stage 4 it will be included in that years final spec, under the new annual review process.)

[1] https://tc39.github.io/process-document/