I am not at mix but I see the BCL team just announced
Silverlight 1.1 Alpha includes all the features available in Silverlight 1.0 Beta plus a number of new features focused primarily on improving developer productivity and power:
- Managed code support
- Support for dynamic languages including Managed JScript and Python
- Rich UI control model based on WPF
- Improved networking stack with support for REST, RSS, JSON, POX
- Enhanced, 2-way HTML/AJAX Bridge
- Comprehensive and consistent base class library
- Support for LINQ (LINQ to Objects, LINQ to XML)
That's right. Silverlight 1.1 Alpha includes support for managed code and a comprehensive base class library! Now you know what we've been up to and why our blog has been relatively quiet these past several months 
Our partner .NET teams within Microsoft have been able to provide an amazing amount of additional functionality on top of the Silverlight 1.1 BCL. There's a networking stack, XmlReader and XmlWriter, an HTML/AJAX Bridge, a WPF API subset, a safe OpenFileDialog control, LINQ, and the new Dynamic Language Runtime (DLR). What's really exciting is that all of these APIs are cross platform and work consistently on both Mac OS X and Windows!
You can download Silverlight 1.1 Alpha today along with the SDK at http://msdn.microsoft.com/silverlight. After you've downloaded the bits, check out the newly launched Silverlight community site. It's a great resource for getting started with Silverlight.
This will indeed be an interesting year. BCL on Mac I doubt Linux could be to far off.
Now we know why many Developers were left with the impression that Silverlight was a little lacking, Microsoft was just hiding their real work.