When Internet Explorer is ready, Microsoft will push it as a "high priority" security update.
This means that Microsoft is going to send it to those who have automatic updates turned on and they will recieve the download w/o user intervention.
Users WILL be given the option to install the new browser, unlike when "Windows Genuine Advantage" was offered.
It is a boldly honest move by Microsoft because they are admitting IE 6 (or any other version, for that matter) is unsafe enough that users are at risk with it. No matter how you view the delivery method or even Microsoft itself, you have to recognize this.
Of course; MS is betting that IE 7 offers enough of an enhancement in security to justify such a "push" installation. Expert opinions are divided on whether it is, though no one I respect has written it is not safer than v6. And you have to remember that any reviews to date are made on code that is being tested and not considered ready for unlimited distribution. Should there be early discovery of glaring vulnerabilities, it will give Microsoft as bad a black eye as it has ever had. If things work out well for the users, I'm not sure MS will get the appropriate credit from anyone but those of us who follow security matters more closely than most. This is because over the years people have formed such a gloomy picture of Microsoft security in their minds that many are unwilling to accept any upward recognition of security in MS' products.