The next stable installer will no longer contain the Sixense plugin that adds support for the Razer Hydra to Interface.
After a new or clean install if you still wish to use the Hydra you can download the archive linked below and follow the instructions contained in README.txt. If you perform an upgrade install (without uninstalling first) your install directory will still contain the Sixense plugin and your Interface will continue to support the Hydra.
http://public.highfidelity.io/plugins/hifi-sixense-plugin.zip