Windows Azure AppFabric has an interesting array of features today that can be used by ISVs and other developers to architect hybrid on-premise/in-cloud applications. Components like Service Bus, Access Control Service and the Caching Service. are very useful in their own right when used to build hybrid applications.
Other announced features such as the Integration Service and Composite Applications are coming features that will make AppFabric even more powerful as an integration tool.
It is important to be able to know where AppFabric is going in the next 2-3 years so that you can take advantage of the features that exist today while making sure to plan for features that will emerge in the future. This research paper from Gartner is an analysis of where they believe Windows AppFabric is headed. Remember that this is an analysis and opinion from Garner and not a statement of policy or direction from Microsoft.