Windows 10: Last of the Lot
Microsoft so far had relied heavily on sales of OS, Microsoft Office and more recently SharePoint Server as their backbone. Newer versions every few years was the way things had been all these years. If I look back, I started my career with Windows for Workgroups 3.11 in the year 1995, which was a significant improvement towards graphical user interface based working experience. Then I worked on Windows 95, which added preemptive multitasking and then on Windows NT that introduced the UNICODE character set. Windows 98, Windows 2000, Windows Millennium edition (that actually disappeared in the millennium).
Windows XP that had some changes done to the visual styles and then came Windows Vista, which got itself the most hated OS rating. It was a generally accepted trend that people would typically skip one version of OS in between, but with Windows Vista, Microsoft had brought too many radical changes. People migrated, but the OS failed to deliver and the performance turned out to very poor. Windows 7 helped salvage the lost grounds and regained the lost popularity.
By this time, another trend in terms of tablets and mobiles was fast gaining traction and there came a tipping point when the sales of Windows OS/PC fell bellow that of mobile. For a while it seemed that Microsoft was in a state of denial and when they did wake up, they delivered Windows 8, an OS targeted towards the tablet world. Where they again did the mistake was to push the same OS on desktops and again their was a large scale public backlash.
Windows 10 is expected to bring back some of the lost charm of Windows 7, while retaining some of the concepts like live tiles added for the tablet/mobile like interface. No more major OS updates after this version means that the idea of being able to push people to new OS every few years is not going to work anymore.
This announcement also has some significant undertones. From a developers stand point, they no longer need to worry about frequent OS upgrades and code migrations. The incremental updates will happen, but will definitely go easy on the developers now. This also means that in time most people will end up using Windows 10, so no longer a worry of supporting a wide variety of OSs, when architecting a new application.
However I doubt that Windows 10 will really be the last OS. It could possibly have a longer shelf life, but over the coming years, I am sure, technology will change further, making Windows 10 redundant and the need for a new OS will be felt. Till then, its wait and watch.