We've seen the light!
Microsoft announced last night (15 April 2007) at NAB (National Association of Broadcasters) the brand name for WPF/E. It will be called (drum-roll)...
Microsoft Silverlight is a cross-browser, cross-platform plug-in for delivering the next generation of media experiences and rich interactive applications (RIAs) for the Web.
Want to see some great samples? Check out http://www.microsoft.com/silverlight/ - bottom of home page.
I'm not a designer at heart, but this DOES look cool.