Here's a further conservative list of low-hanging <Win8 bitrot in the  code itself not already mentioned that can be eliminated as a result of this change, focusing on the Python side of the code and tests; again, I can offer a PR if desired.

Python Code:
* ntpath.py | Win9x (!) | Check for pre-NT versions can be simplified along the lines of the check for darwin in posixpath.py: https://github.com/python/cpython/blob/master/Lib/ntpath.py#L675
* multiprocesing/connection.py | >=Win 8 | Branch can be inlined and outdated comments removed: https://github.com/python/cpython/blob/master/Lib/multiprocessing/connection.py#L866
* pathlib.py | >= Vista | Branch can be inlined and else block removed: https://github.com/python/cpython/blob/master/Lib/pathlib.py#L19


Tests:
* test_winreg.py | Vista | Multiple tests and constants (All the checks and tests requiring registry reflection/`HAS_REFLECTION`):  https://github.com/python/cpython/blob/master/Lib/test/test_winreg.py
* test_winreg.py | <Vista | No-reflection Test: https://github.com/python/cpython/blob/master/Lib/test/test_winreg.py#L309
* test/support/__init__ | <=Win 9x (!) | Test initialization branch can be inlined and out of date comments removed: https://github.com/python/cpython/blob/master/Lib/test/support/__init__.py#L987
* test_winconsoleio.py | <=Win7 | Test branch: https://github.com/python/cpython/blob/master/Lib/test/test_winconsoleio.py#L99
* test_winconsoleio.py | <=Vista | Skipif decorator : https://github.com/python/cpython/blob/master/Lib/test/test_winconsoleio.py#L99
* test_import/__init__.py | <Vista | Skipunless decorator in test initialization: https://github.com/python/cpython/blob/master/Lib/test/test_import/__init__.py#L1025


Other:
* "Since we limit WINVER to Windows 7 anyway, it doesn't really matter which WinSDK version we use." -> can be updated to 8? https://github.com/python/cpython/blob/master/PCbuild/python.props#L101