Windows RT devices won't be upgraded to Windows 10, however Microsoft will continue to update the OS for ARM CPUs with features of the upcoming Windows versions. The information comes from Microsoft watcher Paul Thurrott who reports that Microsoft has told him that "Surface Pro 3 (and the entire Surface Pro lineup) will update to Windows 10". Microsoft also told him, " we are working on an update for Surface [RT and/or Surface 2], which will have some of the functionality of Windows 10."
The software giant from Redmond also promises to come with more information at a later time. Because the Surface, including the Surface RT and Surface 2 are the only systems with Windows RT of which considerable numbers have been sold, Thurrott concludes that Microsoft has pretty much decided to discontinue Windows RT. Also, because Microsoft only mentions the Surface, it's uncertain whether other Windows RT devices, like the Lumia 2520, will even be updated.
Microsoft introduced Windows RT as an alternative to Android for tablets with ARM processors. Windows previously only worked on x86 CPUs, but Intel had only a marginally market share in the tablet market because ARM chips were cheaper and more energy efficient. In order for Microsoft to gain marketshare on the tablet market, the company had to support ARM processors. Intel has now caught up by optimizing their Atoms and subsidizing the processors.
Microsoft has also reported it won't update all its Lumia smartphones to Windows 10, although it's unclear which ones, we expected it will be models with e.g 512MB RAM and storage capacity of 4GB. Their specs might make running Windows 10 problematic.
