Joe Belfiore tweeted this: https://twitter.com/joebelfiore/status/559845609020993536?s=03
Windows 10 branding has the potential to cause confusion. This is my understanding of the future of Windows.
“Windows Phone” for devices up to 8 inches
ARM + maybe x86 support
Windows Phone apps only
Phone capabilities (dialing, SMS)
“Real Windows x86” for devices 8 inches and bigger
Windows Modern apps and desktop apps
No phone capabilities (dialing, SMS)
“Windows RT”: No new devices will be released with the OS known as Windows RT.