I've found this link, the bottom line of which foretells that what I've been using this far to create Office add-ins (i.e. good, old, nice C# code) is to be entirely exchanged for JavaScript.
For instance, we've got a solution that puts a set of buttons on the ribbon and communicates with a CRM server to add data (one in Outlook and one in Word). Will those need to be rewritten as a whole?!
I wish to use VSTO if possible (AddInExpress has been said not to be reliable, apparently). Suggestions?