> So is the proposed change, in a way. At some point, there will be a 4.0 release, which may or may not break the code in question.

I don't think it's a foregone conclusion that there will be a 4.0 release. It could be that we decide that a 4.0 release would be reserved for a very specific kind of major compatibility breakage and that we were never going to do that kind of breakage again.

In any case, I think one part of what Serhiy was trying to say is that we can't just avoid this problem by releasing 4.0 instead of 3.10, because switching to 4.0 brings its own (not inconsiderable) host of problems. Presumably the symlink would be `python4` instead of `python3`, so a bunch of shebangs, documentation and guides would need to be updated.

Basically, unless something changes, a bunch of stuff is going to break in the release after 3.9 no matter what we do. It's probably a good idea to try to mitigate the problems of *both* versioning approaches, to give us maximum freedom in our choice of versioning scheme int he future.