M$ is losing popularity but I doubt it will be Linux that takes the place of Windows if M$ goes under. I love the GNU community to death, but it's a sandbox. End users want completed products. If M$ gives up the desktop OS struggle their place will be taken by some other company that stands on he shoulders of giants (steals GNU work) and charges enormous sums of cash for defective and/or corporate-interest driven products.
Oops, did I talk bad about someone?