I think author is off base - sorry wearables are not it yet.
Life cycle of hardware is such that every piece of computer hardware has built in obsolescence, user replaces their hardware every 3-5 years, components don't last longer than this. So you might have decline in PC hardware purchases granted, but it is not because they received a free version of an OS, it's because they selected another technology that fulfills their needs such as a tablet. If a free OS upgrade was the doom of a hardware platform Apple would not sell new MacBooks or iMacs,Mac Airs, etc...they have not charged for new version of OSX in over 5 OS generations, their hardware has obsolescence built in thats how they do this.
Wearables are not where the money is going either, due to an enhanced obsolescence factor where these devices are old news in 3 months after purchase makes it too expensive for the common user even to consider. Wearable devices such as the Apple watch are also failures; they do not successfully replace or improve on the item they are focused on, your wrist tech. They are parasite devices that can't survive or stand on their own, they need to be paired to other smart devices to be functional, are just too expensive and one more darn thing to charge every day. To make wearable attractive at the current price range they need to stand on their own as the all in one device. Yes it needs to make me my espresso too.