I don't see why you think it's not valid. You're taking an app that was designed to run in the browser, tell it to use different namespaces and it runs on this

I don't see why you think it's not valid. You're taking an app that was designed to run in the browser, tell it to use different namespaces and it runs on this new Metro UI interface, phone, and tablets. You keep the same XAML, same code, and only tweak a few things to make it work on a new platform. It's a similar process to how you tweak your css/js to run in different environments. And what do you mean with existing production code? I imagine you can run still run it in the browser like it's currently working. I'm not a Silverlight developer, but I just can't understand the big commotion. Were people expecting for only SL to work wtih W8? I haven't heard a single thing in the keynote to even hint that SL is going away. Not only that, but they made a point to show that the current investment made in SL paid off. What exactly should they have done?