Surface 2 buyers and other Windows RT tablet owners may be left out of the fun when Microsoft reveals Windows Threshold (a.k.a. Windows 9) at the end of September, as the tipped release is said to be for PCs and tablets built around traditional x86 processors alone, according to a recent report. But when the next generation of Windows does make its way to ARM processor-powered devices, it could provide a startling—and welcome—glimpse at a post-desktop future for Microsoft's "Universal Windows" concept.

While the x86 version of Windows 9 is reported to dial back Windows 8's sweeping changes, introducing PC-friendly tweaks like the return of the Start menu and the death of the Charms bar, the ARM-based version will abandon the desktop entirely, according to separate reports from Winbeta, The Verge's Tom Warren, and ZDNet's Mary Jo Foley.

If true, the move makes sense, as Windows devices with ARM processors are limited to touchscreen-capable tablets and phones, not proper PCs. Microsoft began duplicating desktop functionality in the Metro interface en masse with the Windows 8.1 update released in October 2013.

What's more, both sites report that Windows Threshold for ARM devices will run on tablets and Windows Phones alike, unifying Microsoft's mobile interfaces. Rumors about a potential merger for Windows RT and Windows Phone have been roaring for months, stoked by Microsoft actions such as the introduction of universal Windows apps and a declaration that "We are not going to have three" Windows platforms by former Windows chief Julie Larsen-Green.

Nokia's Lumia 2520 and Microsoft's Surface 2 are the only Windows RT tablets currently available. Other hardware makers have abandoned the platform in favor of Windows 8 tablets with x86 process.

Late last year, Microsoft was also tipped to be working to unify the Windows Store and the Windows Phone Store—an important step if the two operating systems are indeed going to merge.

According to WinBeta's anonymous sources, the ARM version of Threshold will also include the oh-so-sassy Cortana virtual assistant and a notification center, which are two of the 15 features we'd like to see in Windows 9. Both were recently introduced to smartphones in Windows Phone 8.1. Fingers crossed!

Two Windows, two paths

Assuming the reports prove accurate, the changes Microsoft appear poised to introduce in Windows 9 are heartening indeed. Windows 8's greatest flaw was its attempt to force a single interface across a wide range of devices with varied use cases; its successor appears well poised to let a PC be a PC and a tablet be a tablet, a process that was already kicked off by the recent (and superb) Windows 8.1 spring update. The spread-out Start screen is a burden when you're using a mouse and keyboard, while the desktop is a vestigial, difficult-to-use mess on touchscreen tablets.

A Microsoft-supplied screenshot showing the Start menu and Metro apps running on the desktop.

Of course, Microsoft isn't ditching the apps on the desktop entirely. The reborn Start menu will include Metro apps, and those apps will be able to run in desktop windows, as Microsoft revealed at its Build conference this past spring. Again, that falls right in to Windows 9 letting a PC be a PC and a tablet be a tablet—an ideal Apple clearly understands.

Another bonus to these rumors: If Windows 9 truly ditches the desktop on ARM-powered devices, that indicates that we may see those Metro Office apps sooner rather than later. Because there's no way Microsoft would yank the desktop without making a touch-friendly version of Office available for Surface users, right? Of course, Microsoft launched touchy-feely Windows 8 two full years ago and there's still no Metro Office available.

The future of Windows on ARM should be revealed before long. Foley says the Windows Threshold preview for ARM devices is scheduled for next January or February, ahead of an anticipated general release for Windows 9 in the spring.