WCF will provide support with which actions can be enabled for different types to have the same name and includes both serialization of actions with the same name as well as resolution of an action's binding parameter using the new IDataServiceActionResolver interface. WCF Data Services 5.3.0 provides support for modifying the request URL in the OnStartProcessingRequest method. Moreover, service authors will be able to modify both the request URL as well as URLs for the various parts of a batch request. According to official sources, support for instance annotations in Atom payloads will be included in the upcoming releases. Read the full details here.
Microsoft has released WCF Data Services 5.3.0 with support for instance annotations in JSON payloads.