Does Silverlight 4 really use .Net 4 assemblies?

I have gotten a lot of questions from Silverlight users wanting to know if VistaDB will be able to load in Silverlight 4. This would be a great thing if you could actually have a client side database in a Silverlight app. I still am not 100% convinced this is a good idea in most circumstances, but for offline Silverlight apps this would definitely make sense. It would allow you to store data locally in isolated storage on the users machine, and then send it to the server when they next are online. The typical airplane offline app scenario.