What are people's thoughts on automating adding type annotations to documentation now that Typeshed is mature and Python 2 is EOL?
(Let us never speak of comment annotations)

I am not sure if it was discussed earlier there was a discussion on adding PEP 570 syntax across the docs. This comes at the cost of keeping the types updated. There was also a poc over expanding the signature to view the PEP 570 syntax as needed. 

issue37134
https://bugs.python.org/msg344654

Some discussion on similar proposal earlier : https://mail.python.org/pipermail/python-dev/2017-November/150234.html

This was never blocked on Python 2 (at best we'd do this for the most recent Python 3 release anyway).

I expect it will be quite complex to get the quality of the implementation high enough, but I suppose someone should start with a prototype. I'm not volunteering though. :-)

I think a bigger thing is to simply get type annotations to be used in the stdlib first, then we can worry about documenting them as part of the API. :)

Actually I agree with the OP that we could get some mileage out of joining typeshed with the docs, regardless of whether there are annotations in the stdlib.