I did a proof on concept of this with a colleague last year as well, so it was just a matter of time until it was properly release.
The announcement slipped past me as there has not been a lot of whoo hah around it. Reading the release notes for the December 2017 CU for SharePoint 2013 it states:
- Enables the new Document Information Panel feature that's visible in Word 2013.
Maybe a bit cryptic, and I haven’t tested if Word 2013 shows the SharePoint Property Pane, but at least Word 2016 shows it just fine against a document stored in SharePoint 2013.
So, patch away and enjoy SharePoint properties once again in Word!