By July 11 2017, Microsoft is officially ending support for its aged mobile OS, Windows Phone 8.1, which means that users will no longer receive updates.
It is reflected in Microsoft's End of Support page at https://support.microsoft.com/en-us/help/4001737/products-reaching-end-of-support-for-2017
It also marks the end of the road for Redmond’s initial foray into phones, and essentially paves the way for Android and iOS to rule the roost.
Itz interesting to know why they made this strategic move?
Microsoft has been moving away from WP towards Windows 10 Mobile, which is essentially an extension of its desktop platform that’s geared towards letting users take their files and apps with them – but it’s no real rival to Android or iOS. The company has been working on numerous cloud-based and cross-platform apps and services lately, so Windows 10 Mobile doesn’t seem like much of a priority anymore.
In my view, Microsoft is focusing more on mobile cross platform development Xamarin to boost the business benefits of time to market, development cost benefits, easy maintenance, etc.