Python2 will be at end of support next year. That means slowly it will become harder and harder to make calibre runable on modern systems. 3rd-party librays will decline and receive no updates. Python2-interpreter will not be installable out-of-the-box. There will be no security-updates or new features.
Python2 as a platform will slowly die and any application depending on it will die with it. Though, this won't become a serious problem in the next years, but more like 5-10+ years.
To be honest, I doubt corporations will give Python 2 up easily. Currently Python 2 codebase in use in production is probably fairly huge and is just working. Look at how hard it is to convince enterprises to give up Internet Explorer even though Microsoft itself says they should really end using it. Someone like Red Hat will probably keep maintaining Python 2 for at least some years more.
Indeed, but companies have full control over their software and used OS-Versions. They can virtualize, package or even compile themself, and fix problems in their own space.
But calibre is desktop-software, it depends on the OS, the GUI-Framework and whats more... Though, it's actually only a bigger deal for linux, beacuse on Windows and Mac OS is custom to deliver compiled versions from the Project itself. Also there is not wayland-situation on windows and Mac OS, which might break GUI-Libs. But as Calibre has so many different gears it's depending on, there is a good chance that something will break after a certain point.
> Someone like Red Hat will probably keep maintaining Python 2 for at least some years more.
Actually, Red Hat is already dropping python2 for their next enterprise-version as I read. They will probably still have a somewhat maintainend version available somehow, but it's obvious that python2 is slowly phasing out now. And many remaining companies are now starting transition too as EOL is near.
At this point you can already can predict that python2 will have reached minimal levels of usage in 5 years.
Python2 as a platform will slowly die and any application depending on it will die with it. Though, this won't become a serious problem in the next years, but more like 5-10+ years.
It's sad, but the reality now.