Cloud. Windows is going to be sold as remotely accessible virtual machine hosted on Azure. The change will first take place in government offices, then in companies, and finally (after people get used to it at work) among consumers.

Why would gov and enterprise like it? Because of:

• safety - all enterprise data will be stored on Azure servers and won't ever leave it. It makes preventing data leakage so much easier
• maintenance - software updates can be applied even outside of working hours, Microsoft could launch VMs and update at any time
• ease of upgrade - need better specs? you don't need to buy better hardware anymore, you just buy better subscription. Hardware won't become obsolete anymore that quickly

Consumers will also like it. No need to pay hundreds of dollars for new GPU when you just want to play newly released game. Also, all your data accessible from anywhere in the world.

And why Microsoft would like it? Kinda obvious, it would be even harder for users to quit a subscription, they will be tied to ecosystem even more