In a long expected move, Google is now deprecating AJAX crawling scheme.  Googlebot is able to understand AJAX pages better than they could previously, so the support of the AJAX crawling scheme is no longer needed.

When Google initially announced the plan, it was because their crawlers were not executing javascript to be able to crawl and render the webpages.  But since Google now crawls javascript – and all webmasters are recommended to allow Googlebot to crawl both JavaScript and CSS files – Googlebot can generally crawl and render AJAX pages without needing the AJAX crawling scheme.

If you are currently using the AJAX crawling scheme, Google will continue to crawl and index those pages as usual, so there is no hard set deadline where webmasters need to remove _escaped_fragment_ URLs from a site.  But if you have problems, are creating a new site or restructuring a current one, Google recommends no longer adding new _escaped_fragment_ URLs when doing so.