@Alladin: I'm thinking the same thing about XAML + WebCLR as a good replacement for HTML+JS.
Sooner or later we need to ditch the God-awful HTML standard and the God-awful EcmaScript mess that we're currently using as basis for client web applications. Come on, HTML 5 isn't a solution at all, it's simply a patch that's 10 years too late.
XAML as an open loyalty-free standard with some kind of open loyalty-free runtime would have been a great solution here. However, it cannot be Microsoft or another privately-held actor that holds it - it must be W3C or some other neutral consortium.