Patch looks worth merging to me. Some minor questions/quibbles:

Asynchronous iterator question: should the typical pattern for those be:

    def __aiter__(self):
        return self
    def __await__(self):
        return self

"Did we put the ABC's in the right place?" question: reviewing the draft docs meant I just noticed that collections.abc is quite an odd home for some of these. Probably not worth worrying about, given that AsyncIterator and AsyncIterable do belong, and the others are building blocks for those.

The What's New entry can be tweaked to replace "proposes" with "added".