Microsoft announced Windows 8 and mentioned HTML5+JS+CSS often ... but no word of XAML or .NET. So that has caused some commotion. In the end, I get why you would want HTML5 to be the presentation layer for your desktop apps as well. For one thing: how much time is MS spending on web versions and desktop versions of exactly the same thing? Even if you can get them about 95% the same, that's still a big gain.
But it is a huge paradigm shift. And I have this uncomfortable feeling around browsers, even if it is just their rendering engine, becoming part of the OS.
Whatever the future holds I guess :) . MS will not give developers more info until their Build event in September, so until then all we can do is utilize the best practices of keeping UI, UI logic and business logic tiered.