.Net 4 in Windows Phone 7.1 SDK?

Is .Net 4 supported in the new 7.1 SDK?

I am specifically wanting to use the System.Dyna开发者_StackOverflowmic type if available.

I can't find mention of it on MS's sites.

---

It wont be .NET4, but it will be roughly Silverlight 4.

See also: http://forums.create.msdn.com/forums/p/88443/530374.aspx