Update Excel 2016 Volume license customers to a version that supports the latest Office.js version
Excel 2016 customers with volume licenses are locked to version 16.0.4266.1001 which only support the v1.1 API. This leaves out very key API features such as the Dialog API. As these customers tend to be large customers with many installs of Excel, the lack of API support means that it's infeasible for Add-in developers to make use of the new API features and giving up those who cannot upgrade beyond 1.1. A significant UI component such as Dialog API cannot be gracefully worked around and therefore, it's either we use that API and drop support for volume licensed customers or not use Dialog API at all.
There are several threads on the web on different Microsoft related forums about this version. None have been given an answer. A customer working with Office Support was given the answer that the MSI install may never get a version update.
There is no plan to backport the APIs to MSI. But, the good news is that in the new Office 2018, you have support all the way to 1.8.