Although there is no stated expiration for Python 2.7 support, it is bound to end eventually. So I think we should start thinking about a migration to Python 3.3/3.4.
I am therefore opening this issue for the purpose of prompting discussion, and to kick this off with my own initial thoughts.
1. Since a move to Python 3 is a significant change, this is reasonably likely to break some plugins, and so I would propose new version of Picard 2.0.
2. If we are going to have a new Picard 2.0, to which plugins will need to be formally migrated, then we can also take the opportunity to revisit the design of the Extension Points and make them both cleaner and be individually versioned i.e. rather than have a version number for the apis as a whole, we have a version number for each API.
3. I know we will need to make sure that any libraries etc. we use have Py3 versions. Perhaps the most notable of these is mutagen - and according to the later posts in https://code.google.com/p/mutagen/issues/detail?id=27 a Py3 version is available - however I have not check on all the other dependencies.