Conclusion
The schema.org sponsors hope their effort will result in simplicity for those wishing to provide data. The schema.org front page claims:
A shared markup vocabulary makes it easier for webmasters to decide on a markup schema and get the maximum benefit for their efforts. So, in the spirit of sitemaps.org, search engines have come together to provide a shared collection of schemas that webmasters can use. 
http://schema.org/
The aim is to have a single source where a web developer can find all the documentation required to provide information for the big search engines. In principle, the success of schema.org can be judged by two factors: the number of websites providing metadata using schema.org markup and the services provided by search engines that exploit this metadata. Neither of these is easy to judge from outwith the search engine companies, however the indications are positive.
Large scale surveys of the web are difficult, and the results for a new initiative with as much backing as schema.org are likely to date rapidly.  A survey by Bizer et al7 based on data from 40 million websites in 2012, a few months after schema.orgs launch, found that schema.org was used by about 30% of the top 1000 sites. In November 2013 Google were finding schema.org structured data in over 5 million websites8.
It is equally difficult to know what use Google and other big search engines are making of schema.org metadata. What is clear is that any use will be alongside metadata taken from other sources, e.g. the Google Knowledge Graph, data extraction from web crawling and book digitization. The example from Google shopping above illustrates how this information might be presented. Their continuing development of schema.org, for example of the JSON-LD serialization and their use of it in tools such as the Custom Search Engine9, indicates that Google continue to see value in it.
There is a chicken and egg element to these two indicators: web developers will only put more effort into implementing schema.org if they see big search engines using it; big search engines will only use it if they see many websites implementing it. The process can be bootstrapped on both sides. Adoption by providers is eased by support of schema.org by content management systems such as WordPress and Drupal, and extensions providing this support are being developed, as are several stand alone tag generators. In addition, services that demonstrate the value of implementing schema.org can becreated using tools such as Google Custom Search Engine.
