Office 365 is definitely growing significantly – revenue and number of users has increased dramatically in 2014. However, despite the growth rate, the long tail of many years of SharePoint on-premise means that on-premise SharePoint still continues to be dominant across the market.
Redmond Magazine just published the following Forrester Research that shows the breakdown of how many customers are still on legacy versions of SharePoint including a significant percentage of customers with multiple versions of SharePoint still running on premise.
We see this ourselves with many of our customers wanting to move to the latest version of SharePoint either on prem or to the cloud but with lots of challenges in migrating existing platforms. We are currently working with several of our customers to migrate them both to SharePoint 2013 on premise and to Office 365. We expect the growth rate to continue but it will take several years to migrate all the existing customers who have invested in SharePoint as a platform, in particular those with custom developed intranets, public facing web sites or line of business applications that will need to carefully migrated to move to either SharePoint 2013 on premise or to Office 365.