The demise of MS will only lead to better software, more competition, lower prices, and no more annoying unpaid tech support calls from your parents/grandparents/brother/etc.
I'm sorry, I have a problem with this. If anyone honestly expects this to happen then you are frighteningly mistaken. I really hate to point out that Linux needs Windows. It wouldn't be the same beast without Windows, none of this "free and open source" alternative ideal that Linux inspires. Without Windows, the allure isn't there - "the grass is greener" so-to-speak.
There are some god-awful Linux programs out there, don't preach about "better software" - each platform has their good and bad code. How many Linux programs would be crippled or rendered completely incompatitble with a kernel update. It happens with Windows too and automatic updates but you don't see "Requires Windows XP SP2 w/ KB###### and libX" in ReadMe.txt...
More competition, why? What's stopping me from picking up Visual Studio and banging out a Windows program for free and releasing the source code? If anything, there's should be more competition on Windows due to market saturation. I can't argue with lower prices, but what happens when a company decides to release Linux Office 2010 boasting 101% compatitbility with MS Office and then charge $200 for it? We'll be no better off than we are now.
How many of us are going to receive phone calls from family when they can't get printer or wireless drivers? What about a lot of programs distributed only as source? Do you really trust your grandma to be able to compile anything? Even the most noob-friendly distros require a shell prompt and that's where why there's never going to be a "Year of Linux on the Desktop." Though I would love to be proved wrong.