Correct that you need your ZD on at least 9.8.x to support R700 model APs,
...but you may not need to upgrade further, especially if you currently have
7962/7762 model APs, which are not supported past 9.8.x releases. T300
and T301 model APs are also supported on 9.8.3.
The current 18.104.22.168.14 (MR3) is recommended if you don't go higher.https://support.ruckuswireless.com/software/788-zd3000-9-8-3-0-14-mr3-software-release
And release notes say you can upgrade directly from present 22.214.171.124.9 version.https://support.ruckuswireless.com/documents/814-zoneflex-9-8-3-mr3-release-notes
If you wish to someday employ newer 802.11ac model R500/R600 model APs,
your ZoneDirector will require 9.9+ system software. Always check the release
notes for the version you consider upgrading to, for supported model APs.