If you haven't seen yet, the SQL Data Services team announced some excited news at this past MIX conference.  Effectively they have decided to support full relational capabilities in SDS.  Much has been written about this already, including a description of how this will layer naturally with ADO.NET Data Services :).  I recommend checking out these two posts on the SDS team blog:

The no spin details on the new SDS features

Accessing the New Relational SDS with REST

 

-Mike Flasko

ADO.NET Data Services, Program Manager