Just came in here briefly to opine that there is a very real risk of fork if the Python core community does not at least offer a viable alternative expediently. The economic pressures surrounding the benefits of gross’s changes will likely influence this more than any tears shed over subtle backwards incompatibility. I believe it was Dropbox that famously released their own private internal Python build a while back…
I mean, PyPy is over a decade old now, and micropython is a mere 7 years old. What's another fork? If anything, I strongly prefer languages that have more than one implementation.
However, I would speculate part of PSF's hesitancy is likely specifically around the perceived violence that gross' "GIL-less" changes may incur to the runtime semantics' backwards compatibility.
PSF in particular has a responsibility here as well I feel in that CPython is arguably the working spec or standard from which these other implementations work and are defined.
Do you also strongly prefer languages with different underlying concurrency semantics? While stackless and pypy etc. are around and available and this could suggest the answer could be "yes" we've been lucky that they haven't fundamentally changed the experience of writing Python.
The possibility that a ton of libraries might now be able to use efficient multi-threaded execution where they were previously constrained to multiprocessing will be a landslide of changes on its own, and likely reminiscent of python 2 -> 3 compatibility if we have to preserve "two ways of doing things."