IE6 is packaged with XP. A large part of why it's around is that people who bought XP couldn't be arsed to upgrade to anything better.

If some corporate IT department wants to upgrade to Windows 7 but still reinstall IE6 over it for some crufty legacy app compatibility, I think they'll probably have much bigger problems that would make the OS upgrade pointless altogether.

Granted, Windows 7 currently ships with IE8, so we'll still have the same problem for a while.