With my macOS hat on, I don't see a problem with doing this.  C extensions built via Distutils have been version-tagged on macOS since 3.5.0 (for some reason, macOS was skipped when PEP 3149 was originally implemented).

With my release manager hat on, it sounds like a good idea.  But it could introduce a compatibility problem for anyone who doesn't use Distutils to produce extension modules.  So I'd like to see this proposal get a little more visibility, at the minimum, bringing it up on the Distutils SIG mailing list.  We should also ensure that the change gets mentioned in the 3.7 What's New document.  And somewhere in the docset there should be some documentation for the .so file name requirements.  AFAICT, today it's really not mentioned anywhere in the docs other than the reference to PEP 3149 in the 3.2 What's New.  Until the packaging documents for extension modules get overhauled perhaps something could be added to the Building chapter of the Extending and Embedding document:
https://docs.python.org/3/extending/building.html#building-c-and-c-extensions