Almost generic entities, almost working. Include is being ignored. Tested on EF6 alpha3.

AlmostGenericEntities.cs

public class Product
{
  public int Id { get; set; }
  public string Manufacturer { get; set; }
  public string Name { get; set; }
}
public class Camera : Product
{
  public double Megapixels { get; set; }
}

public class Offer<TProduct> where TProduct : Product
{
  [Key, Column(Order = 0)]
  public int SellerId { get; set; }
  public User Seller { get; set; }
  [Key, Column(Order = 1)]
  public int ProductId { get; set; }
  public TProduct Product { get; set; }
  public decimal Price { get; set; }
}
public class CameraOffer : Offer<Camera> { }

public class MyContext : DbContext
{
  public DbSet<CameraOffer> CameraOffers { get; set; }
  public DbSet<PhoneOffer> PhoneOffers { get; set; }
  
  public IQueryable<Offer<TProduct>> OffersFor<TProduct>() where TProduct: Product
  {
    var type = Assembly.GetCallingAssembly().ExportedTypes.First(x => x.IsSubclassOf(typeof(Offer<>).MakeGenericType(typeof(TProduct))));
    var set = this.Set(type) as IQueryable<Offer<TProduct>>;
    return set.Include(x => x.Product);
  }
}