I worked on the first bits for a new Plone development environment. I’ll use this to create a new website for the ODFAuthors team. The new site should run on Plone 5.1 or later. Maybe it is possible to upgrade the site to a Plone version that runs on Python 3.
I read already on a blog of a Plone developer that Core-Plone is already ported to Python 3, but that there are a big bunch of tests that are not yet ported and need some love (and work time).