Hi
Here is a migration guide from Sencha that describes the new features in version 5
If your application uses Sencha's MVC as the application architecture you don't have to change much.
This architecture is still supported in Ext JS 5.
But if the application uses DeftJS you have to change a bit of code.
Here is a description about the changes
The Ext.Direct part (client and server) should work without any changes.
Here is my example application that uses Ext JS 5 and the new MVVM application architecture.
Ralph