If the program continued to only support Python 2, the plugins you mentioned in your post would need to be written in a language which most operating systems so

If the program continued to only support Python 2, the plugins you mentioned in your post would need to be written in a language which most operating systems soon won't have an interpreter for, or will require jumping through hoops to get. Plus, it looks like Calibre doesn't come bundled with a python2 interpreter and relies on the system python2 install, so again, when python2 isn't supported on OS-X and Windows and <insert Linux distribution here>, and your favorite package manager doesn't have a copy any more, that will be pretty inconvenient. With that said, it looks like there are efforts underway to port Calibre to python3: https://github.com/kovidgoyal/calibre/blob/master/README.python3 https://github.com/kovidgoyal/calibre/blob/master/README.pyt...