The release process of these new features is called the TC39 process.
TC39 process has five different stages to get a specification live.
- Stage 0: Strawperson — a way of submitting ideas for evolving ECMAScript
- Stage 1: Proposal — a formal proposal for the feature
- Stage 2: Draft — a first version of what will be in the specification. At this point, an eventual inclusion of the feature in the standard is likely
- Stage 3: Candidate — the proposal is mostly finished and now needs feedback from implementations and users to progress further
- Stage 4: Finished — the proposal is ready to be included in the standard
Next time you want to use a new feature, check the stage before put it in production.
TC39 urges caution when using Stage 2 or below proposals.
By the way, you can see a list of proposals here, one of my favorites is Optional Chaining.