We are excited to announce that we have launched our new Hive Community! HiveNation will remain as an archive, but all new posts, discussions, and articles will be created on Hive Community. You can visit our new community at thehivecommunity.aerohive.com
At the moment, you should upgrade to HiveOS 6.4r1a for HiveManager-NG.
HiveOS 6.5r1 is, I believe, for the newly announced AP130s only.
HiveOS 6.6r1 is due around June this year. This release should, I believe, include the AP370 and AP390 assuming that everything goes to plan from a development and testing perspective. (Implied in the Ghost advisory.)