This is a tracking bug for issues that need to be done when pywikibot supports Python 3 only. On basis of T213287 and there is a suggestion to create a new repository for a further pywikibot 4.0 which takes into account that it was desired (see T221801) not to have a deep impact of breaking changes when dropping Python 2.7.
In favour of making a new 4.0 branch having a new repository seems easier to handle. There is no need to exchange a 4.0 branch with master and the current master to 3.0 branch later and the current pywikibot-core is still accessable (like pywikibot-compat is also still availlable). The old repository can be set to read-only when developers are going to support the new 4.0 repository.
First of all we should find a new repository name if this proposal is ok. Suggestions are welcome.