Well, not yet and maybe not replace, but certainly with time eat more from their share. For example, Howard County Public Library, MD has just installed 80 linux stations. That means - 80 Windows VISTA licenses and also - 80 MS OFFICES. People will go, with time learn how to use it, try it at home and then maybe buy wii for their kids to play on. Nobody says Windows will disappear, but Linux will surely eat a big chunk of their market. Plus, let's see how those 100-150 USD notebooks do when they are finally launched. I've just upgraded to Ubuntu 7.04 and I love it. I also use Windows XP, but not that much.
Man Rui