I have to agree with the parent, this just seems like the initial Java hype all over again. Not to say that Java is a bad concept, but it simply hasn't achieved what some of its early proponents thought it would.
In terms of the article itself, the author has clearly got caught up in the hype and forgotten that:
a) Microsoft's core market is the business market, not the consumer market.
b) Even if they would go for it, big software houses would be very uncomfortable writing applications which anyone could view the source code of and rip off.
I mean, try telling enormous ERP vendors like SAP or Sage that they need to rewrite their software in HTML5 + JS. Yeah, sure, they'll get right on that. Companies have huge investments in traditional applications (as opposed to 'apps') and that's not going to change anytime soon considering most of the big players still consider .NET to be new and fancy, especially not when it threatens their IP. Not to mention that the article completely neglects to think about the Windows Server product line - do they seriously expect people to be writing server-side applications in this way?
My prediction is that we'll see a few HTML5 weather widgets to go on the tiles interface and that everything else will continue down the .NET line. Maybe by the time Windows 8 see widespread business adoption sometime around 2020 then there'll be a couple of HTML5 intranet widgets and company stock tickers too, but the idea of all software going this route anytime soon is pure fantasy.