Our End of Life policy is defined in our Support Services Policy, and explains that every release of Elastic's products (Elasticsearch, Logstash, Kibana, Marvel, Shield, etc.) has an 18 month life span. At the end of that 18 month period, no future releases for a version that has reached EOL will occur since no current or future development will happen. Effectively, once a version reaches EOL that version remains frozen and unchanged forever.
From a support perspective, a release is fully supported right up till the EOL date. Beyond that date, however, our ability to assist you will be greatly diminished. You can expect the following kinds of help for an EOL version:
Knowledge Base/Known Issue: We will continue you point you to known issues/workarounds and/or articles that could help you
Upgrade Assistance: Known issues in a version that has reached EOL will never be fixed in that version but is most likely resolved in a current version
Beyond the above types of help, unfortunately there is no more we can offer for a version that has reached EOL.