Office 365 is accelerating that. No need for local Word, PowerPoint, Excel, etc.
I'd guess Microsoft gets most Windows sales from regular people buying regular laptops with Windows preinstalled. Most of them probably don't even know there is something else other than Windows.
I instinctively feel like ChromeOS and OSX (and mobile OS variants) are going to kill Windows desktop off. But I'm also aware I might be off base.
Around here ChromeOS is a kind of rare animal hardly seen on any consumer shop, and when it appears it is usually tied to some promotion to get rid of those in stock.
OS X is everywhere on northen Europe big cities, but go south or to the country side where many people dream to go over the 500€ barrier and it too becomes a rare animal.
Maybe it's because a computer is a significant expense, so people value price/performance more,
or maybe because schools have Windows PCs and nobody is used to OSX from young age.
For gaming, it's pretty much only choice, Macs have no hardware to handle them, and for Linux, I've tried switch many times, and it always been a hassle.
I've ended up with Ubuntu for work and Windows for everything else.