A couple of years ago Microsoft surprised everyone by making a version of Windows 8 for ARM but efforts to kick off this new ecosystem failed as OEMs and consumers largely ignored Windows RT devices. So it doesn't really come as a surprise that Windows RT has no future, Microsoft has no idea how to fix RT and will instead grow its ARM support via the Windows Phone lineup.
The software giant said Windows RT users will continue to receive some unspecified feature updates in the future but they won't be getting an update to Windows 10.
The non-adoption of Windows RT was a perfect storm of poor decisions at multiple levels of Microsoft. The Tegra 3 SoC that powered the first generation Surface RT didn’t pack enough horsepower to really drive a top-tier tablet experience. Microsoft did a miserable job communicating the differences between Windows RT and traditional x86 Windows, tales spun of consumers taking the hardware home, firing it up, and then returning it when they realized they couldn’t run desktop applications.
In retrospect, Microsoft’s decision to retain the desktop for Windows RT was a huge mistake. While it’s true that the desktop offered certain functions that the nascent Metro design wasn’t ready to replace on launch day, the sight of familiar icons and desktop interfaces primed consumers to expect the same degree of software compatibility and flexibility. Stripped of those features, Windows RT lost much of its appeal.