Starting April 6, data-vocabulary.org structured data markup will be ineligible for Google rich results. Site owners have to switch to schema.org markup if they want to maintain Google rich result eligibility.
If you don’t convert to schema markup, your rich results are going to disappear from the search results page after April 6, and as a result, you will loss organic visibility and traffic.
According to Google, the company is focusing on schema markup because of its increasing usage and popularity.
Site owners can use Google’s Rich Results Test tool to test live code snippets.
This change only pertains to rich results. Pages using data-vocabulary.org markup for other purposes will still remain valid.