I know it will happen. It will just take IT managers who grow up in this generation for it to happen. Remember, there were managers who came up through the "You can't get fired for buying IBM" generation. Most of these have been replaced with a new generation of managers who are from the "You can't get fired for buying Microsoft" camp. Only now are we starting to see IT managers who are part of the open source and Google generation. They will be the ones who move their IT infrastructure to the cloud.
Technology in your organization is usually a reflection on the management who make those decisions.