According to this post from the Astoria Team Blog, it looks like we won't have a new Astoria (ADO.NET Data Services) client for Silverlight 2 until SL2 Beta 2 is released (perhaps May 2008?)
Many of the data demos for Silverlight 2 have so far used LINQ to SQL for the data access layer. These demos involve creating a LINQ to SQL data model (using a nice drag/drop editor), and then exposing that model through a web service by manually coding a WCF Web Service or .asmx Service.
Don't get me wrong, this is a pretty rapid development method... but what if you didn't need to code the web service for basic CRUD operations and queries on your data? What if it were all exposed for you and you could use LINQ to access the data from the Silverlight client?
This automatic service layer is just one of the advantages that ADO.NET Data Services (Astoria) provides, and since Silverlight 2 has much better support for Data Entry controls, the combination of SL and Astoria should provide a powerful rapid development environment!