In the build-up to Windows 8, one of the many mini-controversies that Microsoft found itself embroiled in involved the creation of "Windows on ARM," later called Windows RT, the ARM-based version of the firm's flagship OS. Microsoft has rarely made a credible case for why it even needed a Windows RT, and of course Windows RT-based devices have sold poorly. Fortunately, the firm now has a plan to consolidate its Windows lineup.

The catch? We don't know what the plan is exactly.

But we can guess, based on some recent and illuminating comments from Julie Larson-Green, the executive president in charge of Microsoft's Devices and Studios group. Looking at her direct responsibilities—all in-house hardware development (Surface, Xbox), as well as games—it might not seem like Larson-Green is the best source for this information. But after many years as the second-in charge for Windows 7, 8, and 8.1, and now the most senior executive directly responsible for Surface, she's of course in the know. So her words carry weight.

In an appearance at the UBS Global Technology Conference last week, Larson-Green was deliberately cagey about Microsoft's plans. This makes sense: The firm just launched Windows 8.1, which includes a major new update for Windows RT as well, and has plans to deliver a Windows Phone 8.1 update in the spring. So this is no time to drop the bombshell that everything is about to change.

But she did offer this: "We have the Windows Phone OS, we have Windows RT, and we have full Windows," she said. "We're not going to have three. We do think there's a world where there is a more mobile operating system that doesn't have the risks to battery life, or the risks to security. But it also comes at the cost of flexibility. So we believe in that vision and that direction and we're continuing down that path."

Rumors about such a change have been making the rounds all year. In October, Mary Jo Foley reported that Microsoft was planning a new unified Windows OS strategy spearheaded by Mr. Myerson.

But critics have been wondering for some time now why Microsoft continues to develop multiple versions of Windows—"full" Windows, Windows RT, and Windows Phone, although of course there are others, including Windows Server and of course variants such as Azure and various embedded products—while its competitors, such as Apple and Google, offer more simplified product lineups.

Honestly, I'm not sure what all the hand-wringing is about. Most of what we think of as Windows today is, well, Windows. Windows 8.1/Server 2012 R2, and Windows Phone 8—and even the Xbox One, really—all run on basically the same kernel and share many technical underpinnings. Mixing and matching even high-level apps between them might not be trivial, but it's certainly possible.

More to the point, the only real oddball in that group, when you think about it, is "full" Windows—that is, Windows 8.1/Server R2—because those systems still include the desktop environment as well. If I'm understanding Larson-Green's comments, what Microsoft is working toward is essentially "two" Windows—really, two families of Windows—that we might divide into the desktop haves and the desktop have-nots.

And I think the have-nots are going to be consolidated. Some have taken this to mean the end of Windows RT, and they present as evidence the fact that former Windows Phone chief Terry Myerson now runs Microsoft's overall operating systems efforts. And he's been making moves to remove former Windows executives from his team in recent months.

I'm not sure this is the correct way to read the changes. I think a more accurate view is that Windows Phone and Windows RT will in effect be merged and that no matter what the resulting name of that products is—how about "Windows"?—it will simply be a single platform that runs on mobile computing devices from phones to phablets to tablets to hybrid PCs, with just software-based changes necessitated by differences in the form factor or mission of the devices on which it runs.

I'm looking forward to this change. Both RT and Phone offer some things that would benefit the others. And combined, this makes a new "Windows" all the more interesting.

Of course, many of you are probably wondering about "full" Windows and the classic desktop environment. My guess is that it will stick around as long as there's a demand for it. (Larson-Green said at UBS that she expected the desktop to continue "for [her] lifetime.") That demand will be there as long as the non-desktop Windows isn't mature enough to handle most needs. And even this expected combination of Windows RT and Phone is just a step in the new direction.