Seeing a lot of people shocked by these tweets. If this comes to pass, it really shouldn't shock anyone. This is the model that Microsoft CEO Nadella has been working on for years. He was in charge of cloud infrastructure, client services, and overall services. He was crucial in migrating Office from stand alone software to service-based subscription. Enterprise Windows 10 is more of a service than an OS at this point and there's no reason to suspect that they won't be doing the same thing with home versions later on in its lifespan, once the adoption rate is high enough to justify doing so.
Nadella has never really been a big "hardware" guy. Under his "embrace-and-expand" philosophy, he basically undermined ALL of Microsoft's attempts with Windows Phone by taking every major exclusive feature and rolling out similar software versions on Android and iOS (Office Mobile, OneDrive, Xbox, etc.). Migrating to services has been Nadella's entire plan since taking over after Ballmer.