I looked into a migration of the ODFAuthors site to a current Plone version with the data from the website yesterday. It took me a lot of hours to figure out the most easy way to do this. I tried to migrate from LinguaPlone to the new multilingual Plone plug-in first, but without success. I could update the buildout inside a test environment with the new plug-in, but I wasn’t able to migrate the content to the new framework. And even I wasn’t able to get rid of LinguaPlone. I didn’t get the option to remove it. I got always a traceback and found some users that run into the same issue without a solution. Thus I had to change my strategy. I exported the content that I need to migrate, set up a new and clean Plone 4.3.x environment and tried to updated it to the latest version of 4.3. I had to do some editing on the buildout and had to drop some Plone add-ons from the current buildout script of ODFAuthors. Once I had done this the buildout runs fine and I got a clean new Plone environment. Then I added the plug-ins plone.app.contenttypes and Products.contentmigration to the buildout script and run buildout again. I started the Plone instance, created a new Plone site and imported the content (exported from the current ODFAuthors site).
I activated the plug-in plone.app.contenttypes and run the migration scripts from Products.contentmigration. I had to migrate more than 4200 content objects and took a fair amount of time. But in the end the migration from the old Archetype content types to the new Dexterity ones was successful.
The next step would be the migration of the instance from Plone 4.3.x to Plone 5.0.x or 5.1.x.