Lots of big players still use Python 2 (Google being the most prominent), and untold smaller players.
Besides, Windows XP and PHP are also in use, as are 50+ year old COBOL systems, so there's that.
Unless you come in and do the port yourself, many systems are not getting ported anytime soon. RedHat and co will continue to release 2.7 patches for the foreseeable future, long after 2020.
Also Google have golang, which I'd imagine would be their target now, not python 3 (for migrations)
I don't think the "many eyes" theory ever panned out. There are projects used by billions, and on which thousands of other FOSS projects work, and only have like a handful of people working at the codebase (and less catching bugs)
>Also Google have golang, which I'd imagine would be their target now, not python 3 (for migrations)
Not really, Golang was never Google's official/mandated language. Just a language some Googlers made with Google's use cases in mind. Google still uses C++, Java, and Python (plus some Dart). Some things use Golang, but not in some top-down "Googlers shall use Golang" way.
Build system automation of all kinds (although the main build tool is in Java)
Test automation
Deployment automation
Many services configure their job placement and options with a Python-derived language (not mine)
Monitoring configuration and dashboards
Data analysis using Scipy, Scikit, Numpy and various kinds of notebook UIs
Configuring Tensorflow and analysing the results of ML projects
Hundreds of little command-line utilities for all sorts of small code and data manipulations
Thousands of internal websites
The youtube.com site was still Python last time I looked