For Enterprise Customers using Office 365 ProPlus, users will be migrated to the latest version in February of 2016. If you want your users to stay on Office 2013 and continue to receive 2013 security updates, you can delay their migration to Office 2016 ProPlus. Your users will continue to receive security updates for Office 2013 ProPlus until February 2017 through the same update method you are currently using. However after that time, no additional security updates will be made for Office 2013 ProPlus, so we strongly recommend that you migrate to the latest version before February of 2017.
There are three ways we can delay the migration to Office 2016 ProPlus, The first is to use a GPO setting that blocks the update or you can push out a registry key manually that will do the same. Those options are outlined in our KB here:
Thirdly, we can use the Office Deployment Tool (ODT) and the configuration.xml file to prevent the migration as well.
In the configuration.xml file we will add the AutoUpgrade attribute and set it to "FALSE" like in this example configuration.xml file here:
<Updates Enabled="TRUE" AutoUpgrade="FALSE" />
The Office Deployment tool was updated in December of 2015 to accommodate this new switch. If you are using the old version of the tool you can download the newest one here.
Prepare to update Office 365 ProPlus to the Office 2016 version