I think ultimately the developer community and not Microsoft will decide what will get more support. Microsoft did not invent HTML5, they were practically uninvolved in its development at all. The reason they are backing it is because everyone else is. Google is writing a whole OS around HTML5 and other web technologies.
People do use web apps so much these days, hell I'm using a web app right now - it's called Channel 9. Microsoft really has no choice but to be all in with this technology and make it a first class citizen in Windows. It's really the developer community and ultimately the users who decide, and the whole developer community is much larger than the .NET developer community.
I don't see the same advancement there for .NET, other than "I'm still here". That's great I guess. You guys can celebrate that, you are not completely dead in the water. But I wouldn't be surprised if WinRT is a net regression over WPF and .NET proper.