> I guess is the objection of putting concrete ABCs in the abc module is that the abc module contains the actual code to implement ABCs and not ABCs themselves.

I think it's a rather weak objection.  Having some basic (and fundamental!) ABCs defined along with ABCMeta won't hurt.

> Personally I would be fine with a submodule within abc like abc.interfaces.

> Personally I'm starting to warm to the idea of sticking ABCs in proper packages as e.g. functools.abc for Callable; namespaces are one honking great idea after all. :)

It will be hard to find proper namespace for things like Hashable and Awaitable.  That's why I like the idea of putting them in the top-level 'abc' module.