Plone 5.2 supports Python 2.7, 3.6 and 3.7. It is based on Zope 4.x and runs WSGI. These three are major changes under the hood but have only limited effect on end-users and development of add-ons.
Plone 5.2 comes with many bug fixes and a couple of nice improvements. Here are some noteworthy changes:
New navigation with dropdown. Site-Administrators can use the navigation control panel /@@navigation-controlpanel to configure the dropdown-navigation.
New Login. The old skin-templates and skin-scripts were replaced by browser-views that are much easier to customize.
Merge Products.RedirectionTool into core. Site-Administrators can use the URL Management control panel (/@@redirection-controlpanel) to manage and add alternative URLs including bulk upload of alternative urls. As an Editor, you can see the URL Management link in the actions menu of a content item, and add or remove alternative URLs for this specific content item.