EOL (End-of-Life) term was just announced.
Only up until Sept. 28, 2016, Zend Framework 1 will receive security updates.
"With the release of Zend Framework 3, it's time to halt development on Zend Framework 1. As such, we hereby announce that Zend Framework 1 reaches its End of Life (EOL) three months from today, on 28 September 2016."
Read the official announcement.