He might have been just using that as a rough number for example purposes. Python does use semver loosely (effbot.org&#x2F;pyfaq&#x2F;how-does-the-python-version-numbering-schemae-work.htm).<p>I expect there probably will be at least some breaking changes in 4.0 or at least major new additions to warrant the major version bump, but I think they want to avoid anything that makes migrating code&#x2F;libraries anything more than trivial for the majority of users. For 2-&gt;3 stuff like print as a function was straightforward, but other stuff like lazy range() or the Unicode strings would actually require people to make significant changes, which stagnated migration.