This is a significant change to the language.
There should be a PEP, or at the very least a discussion on Python Dev.

There may well be a very good reason why static methods have not been made callable before that you have overlooked.

Changing static methods to be callable will break backwards compatibility for any code that tests `callable(x)` where `x` is a static method.

I'm not saying that making staticmethods callable is a bad idea, just that it needs proper discussion.

https://bugs.python.org/issue20309 was closed as "won't fix". What has changed?