We decided this fundamental approach was a failure, and are instead focusing on the opposite approach: designing and writing applications for the browser and then also running them in a desktop environment. Applications designed for the more limited browser environment tend to behave quite well when run in a browser widget in a traditional desktop application. — link
I think you will see more and more web based support as Eclipse matures. These “widgets” will be available in both RCP and Web based applications. Check out the Open Social Specification 2.0 and specifically the Gadget and container API’s being presented. They will allow even further integration of web based Open Social Gadgets with rich client applications.