Seeing the [first announcement of the HTML5/JS Windows 8 GUI](http://windows8news.com/2011/06/02/microsoft-unveil-windows-8-tablet-ui/), plenty of [WPF and Silverlight developers panicked](http://forums.silverlight.net/forums/p/230502/562113.aspx).

What is the future for these technologies? How will the new and old technologies be able to cooperate? Should we all start developing using an entirely new framework pretty soon?

Does anyone have official sources clarifying the situation a bit?