Google has Grumpy. Because writing a compiler is easier than porting. https://github.com/google/grumpy

Not sure about that. Some companies may have codebases as complicated as the python codebase itself. For them it may make more sense to maintain python2 than to upgrade. Granted, there will be very few such companies.

Python 2 is popular enough that someone will keep up support for decades to come. Just making sure it supports new OS releases, and fixing the occasional bug, will not be a significant overhead.

Unjustifiable assertion.

  - they could continue to maintain python2
  - they could move to a non-python platform
  - they could go out of business
  - they could hold out for Python4 (Python3 was only 8 years after Python2)
  ...

GVR has already said that Python 4 (if it's even ever called that) will not have the same kind of breaking changes 3 did.

And 3 had different changes than 2 (https://docs.python.org/3/whatsnew/2.0.html) though it is interesting that Unicode support was a big feature in both, and that many people still find Python3’s Unicode support problematic (e.g., http://lucumr.pocoo.org/2014/5/12/everything-about-unicode/)

But if an individual or organization does not find the python 3 updates and ecosystem a compelling upgrade over 2, “don’t update until the next big change” is definitely one option.

The whole point of my comment is that there won't be a "next big change", just lots of smaller ones.