Twenty years ago Windows 95 launched and dragged the whole world into the modern age of computing. Whereas what had gone before was either complex and difficult to manage (Windows 3.x) or limited and poorly conceived (Macs OS 7) Windows 95 was simple to use and took a large leap forward in insulating the user from the technology. It was hugely successful and its legacy has been an almost totally homogenous computing landscape built around Windows.
A feature of Windows (and all other operating systems) since then has been the new release. That is a concept that ends (for Windows users anyway) when Windows 10 ships to consumers. Microsoft is talking about Windows 10 as Windows as a service. So in the same way that Office 365 continually receives new updates and features so Windows will do the same.
One note of caution however. For those users who buy machines that have been sat on a retailers shelf for several months the application of all of those updates just after buying a new machine is a miserable process which hurts the first impression of Windows significantly. I know several users who have had the same experience with Windows 8/8.1 and sworn off Microsoft for life after having to wait hours or even days for a new machine to bring itself up to date.
So however good the plan for Windows as a service might be, without a strategy for dealing with these issues when setting up new, but out of date, machines; Microsoft may yet be doing itself more reputational damage.