Albeit, that the specification of the emerging coding tool, HTML5 are still awaiting finalization. How developers would embrace tools termed less capable, renouncing their current platforms, may well put Windows developers at lurch.
Microsoft, earlier made available the F12 HTML tools in Internet Explorer, but until generally accepted a tooling for HTML5 on that platform, the traditional tools remains indispensable.
Definitely, Microsoft's ultimate aim of weaning developers off traditional Windows tools, perhaps will have to wait, at least for now. Microsoft's support for Silverlight will continue, and not just as a browser plug-in, among other things.