The <noscript> tag was notoriously buggy and iritating cross-browser, so I can see why they wouldn't want to implement it, like the <blink> tag.
If you use something like modernizr, which replaces the "no-js" class on your <html> tag with "js", you can just have a <div> or <p> simulate what <noscript> would have been. Have it "display: none" if the element is a child of "js". (trick courtesy Paul Irish)
For a quick summary/reference: http://javascript.about.com/od/hintsandtips/a/Html-5-And-Nos...
