This generation of computer users is a bit smarter than their parents. I have faith that the security issues with Windows XP, and the ones that will be created with the new features in Longhorn will cause quite a few users to come our way.
The ones that adapt will stay. If they cannot they will rot in Windows world. I cannot stress enough though, that gaining Windows users is not worth becoming Windows like to the point that users who like a real Linux desktop will look to other desktop environments and distros.
The average Windows using, webshots using, download.com free Christmas wallpaper/screensaver user isn't even going to file bug reports. While we want them to use the OS, catering to them to the point where Linux users are pushed to more configurable/powerful distros and desktop environments would be folly.