It is not necessary to have Word 2016 through an Office 365 subscription to receive updates. On the other hand assuming that at sometime there will be a Word 2017 or 2018, it is only will an Office 365 subscription that you
would receive the new version.
True, all 2016 versions get bug fixes and security "updates". But the point that Suzanne is making is that MS will probably not treat this as a simple "update" that goes to all Office bundles. She, and I agree, suspects that MS will treat this as a "new
feature" that will only be distributed to Office 365 (their not so subtle way of "encouraging" hold outs to switch to the more profitable subscription license s**m.) One-time payment 2016 licenses will not get it. For one-time licenses it will only show up
in the Next version of Windows that will be released in 2018/19/20, or whenever.