Poetry helps alleviate some of the issues mentioned here, and lets you separate dev vs prod dependencies. As far as the "new PHP" goes, it'd be great if Python ever powered almost 80% of websites: https://kinsta.com/blog/is-php-dead/

Docker has been the saving grace for Python. I once used to build deb and rpms of a Python project of mine and I'd rather stick a finger in my eye than go through that pain again.

Probably never. PHP is at least generally simple to deploy.