> As to using pip to build wheels -- there is good reason to do that
> now, but in s post PEP 517 world, one would call the build system
> directly to build a wheel-- after all, all pip should be  doing is
> calling the build system anyway.

I disagree - "pip wheel" will still be useful, for example to obtain a
wheel from PyPI either by downloading or download & build. Also just
to have a unified interface that works regardless of the project
backend - if a project switches from setuptools to flit, for example,
it would be good if deployment and test scripts didn't have to change.

So I still expect pip wheel to be useful in a post-PEP 517 world.