World is moving on
The world is moving on from installed applications, not fast but it is.
MS see this and have brought to the market Office 256, with a ROI of 1000%, trying to stave of Google bridge head with Google Apps. Users will drive this as they will want the same experience they have with their tablets and smartphones. Which is provided by Google Apps but not by Outlook. Businesses large and small will want this as they can make saving and deploy IT staff on more productive tasks.