Pages with #! will no longer be supported by the Yandex search engine. In order for the content to be available to users and not disappear from the search results, you need to set up a 301 redirect from such pages to new ones with correct addresses (namely, without the #! parameter).
You need to set up a redirect both from pages to addresses like http://www.example.com/?_escaped_fragment_=blog, and from pages like http://www.example.com/#!blog.
Pages with the “meta fragment” tag will also stop being indexed soon, so it is recommended to check the rendering technology for them and adjust it in Webmaster if necessary.
In more detail about what will happen to AJAX pages in the future, the Yandex team will report separately in the near future.