Linux is here to stay I believe, but I don't think it will necessarily be dominating the desktop anytime soon. I have used Linux enough to know that anybody who thinks it's going to take over the desktop market, especially on the home front, is crazy. Many people see the computer on the same level as a TV or toaster, and they just want to turn it on an do what they want. Windows, while it does have problem--like any OS, is much easier to use than Linux. While I personally don't like or want XP, I certainly see why it would be appealing to more than just a few computer users.
I don't think Windows is going down any time soon. Linux has potential, but it also needs some work before I really would consider it for home use.