Looks like the latest development in the bumpversion saga is another project change:
bump2version
Bump My Version
Figured you might be interested to know, especially since the new project supports pyproject.toml. Out of curiosity, are you using tbump in your projects? I would like for my version bump, commit, and tagging command to include auto-generation of my changelog. It appears that tbump may be better suited to doing that for me, rather than me having to hack in some sort of git amend script around the bump[2]version command.