Google announced that it’s okay to merge two kinds of Schema.org structured data now and that it will validate at the major structured data validators. Now your choices aren’t restricted to exclusively using JSON-LD or Microdata structured data. JSON-LD structured data is preferred because it’s easy to maintain, easy to read and troubleshoot and is separate from the HTML. Now you can communicate to Google what the main content is (when using the Article structured data) with Microdata format of structured data without having to create a duplicate of all the content inside of the JSON-LD structured data. This change isn’t mandatory, you don’t have to change your current JSON-LD structured data.