Google will likely be expanding implementation support for rich snippets through JSON-LD. John Mueller confirmed this on Twitter after a webmaster said he saw websites using JSON-LD to power their product reviews rich snippets. Using JSON-LD is not in Google’s help documents for rich snippets but John Mueller said they are looking to expand it in the near future. Here is John’s tweet:
@JohnMu Would you recommend changing an existing JSON-LD implementation if Rich Snippets already appearing in Search Results? Any Risks?