You can still continue to use your EndNote software. If you need to immediately use the Cite While You Write tools with Word 2016, you can simply downgrade your Word installation as outlined here:
https://support.clarivate.com/Endnote/s/article/EndNote-Word-2016-Mac-version-16-Compatibility
When you start EndNote X8, it automatically checks for updates. When our update to address the Word 2016 16.9 update release is available, you will receive notification in the software. You can also manually check for updates by clicking the EndNote menu and selecting Check for Updates.