The argument goes something like this:
All of a sudden, the public (in the US, at least) are hearing the idea that IE is "dangerous" in some way from an organisation that they've heard of.
Microsoft, naturally, are urging CERT and the DoHS to 'clarify' the advice (which must mean they're worried).
Family members are starting to ask their captive geek what alternatives to IE actually exist.
IT departments are starting to look seriously at replacing IE on the desktop in favour of Mozilla/FireFox/Opera/etc
ie, Death of Microsoft predicted, unsigned ActiveX control at 11!
Much as I might welcome the obliteration of IE from the face of the Internet, in favour of something that was more - say - 'receptive' to the idea of web standards, I don't think this hoo-hah about the latest set of vulnerabilities will be the trigger.
Undoubtedly a number of people will act on this spur to finally give something else a go, but the majority either a) won't even hear there's a problem b) won't know what to do about it or c) will get distracted in the process of trying to do something about it.
Max Planck had it right when he said in his scientific autobigraphy that:
a new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it
and Thomas Kuhn expanded on this theme in his 1962 essay "The Structure of Scientific Revolutions":
When discoveries create crisis situations within a scientific community and push the limits of an accepted paradigm so much so that scientists begin to deem the paradigm untenable, the community must begin to look for alternative paradigms.
The paradigm shift that's just around the corner in this case is the next generation of 'computer' users. Instead of having been directly involved in the explosion of technology over the last 40 years (and suffering and enjoying the consequences in equal measure), it's been part of their landscape since day 1.
The death of Microsoft (slow and lingering though it may be) will be as a result of this generation wanting and expecting their technology to a) be cool and b) just work.
Although the argument can be made that certain MS-based technologies 'just work', I'm not sure it can ever 'be cool' in the same way that - say - DJing a gig with a pair of iPods is.
So no great Chicxulub extinction event to look forward to, just a gradually more pervasive disinterest in using something that doesn't inspire.