2018-02-07 – We have successfully completed and tested an upgrade to Zimbra 8.8 on our development platform. This platform closely matches our production Zimbra platform. We will be testing new Zimbra features for compatibility and closely monitoring community feedback and Zimbra support feedback before we announce an upgrade date.
2017-12-14 – Zimbra version 8.8 was released yesterday (13th December 2017). We have published our plans for migration here