Co-Authoring for Semi-Annual channel

Approximately January 2019! The new semi-annual (targeted) came out on March 13. This build contains the feature set that will be released in the July 2018 update, and co-authoring didn't make the cut. So it looks like Microsoft will push this one out during the January 2019 release instead.

Semi-annual (targeted) release notes: https://technet.microsoft.com/en-us/office/mt465751.aspx

Explanation of channel release windows: https://docs.microsoft.com/en-us/DeployOffice/overview-of-update-channels-for-office-365-proplus#visual-representation-of-the-update-channels-for-office-365-proplus