In many ways mobile technologies are derivative of their desktop brethren. Your iPhone’s e-mail app is like the e-mail client on your desktop, for example. The mobile world is the desktop world in miniature, a “lite” version.

But the mobile world is no longer just following; it’s leading. PC sales are sagging, while sales of mobile devices—smart phones and tablets—are on the rise. As the operating systems that power these devices become the new norm, we can expect to see certain aspects of desktop and laptop operating systems start imitating the little upstarts that had initially imitated them.

This transition is already happening. Apple’s Mac OS X Lion includes the Mac App Store, full-screen apps, and multitouch gestures. Apple also recently announced a big developers’ conference in June, during which it said it would “unveil the future of iOS and Mac OS.” Other companies are following similar paths of convergence. Though Google’s Android (for mobile) and Chrome OS (for laptops) have notable differences, CEO Eric Schmidt has long maintained that “although it appears they are two separate projects, there’s a great deal of commonality. Eventually they may merge even closer.” HP’s webOS, which the company acquired when it bought Palm, is designed for mobile use, but it will also be coming to notebooks and desktops. And we have reason to believe a similar convergence is on its way with Windows 8.

“It’s very likely that PC operating systems will be affected by mobile devices’ operating systems—and more broadly, that the lines between the two will increasingly blur,” says Michael Dahlin, a professor of computer science at the University of Texas, who has expertise in operating systems. “Things have evolved to the point today where the difference between the smart-phone OS and the laptop and desktop OS is narrowing—and really already pretty narrow in terms of capability and core architectures,” he says.

This trend is nothing new in the history of technology. In the case of mobile and PC operating systems, however, Dahlin thinks another factor is speeding it along: the cloud. “The cloud is part of what’s going to enable and probably drive convergence between phone and mobile operating systems and desktop operating systems,” he says. Now that a user’s data isn’t necessarily tied to a particular device, manufacturers feel they’ll be expected to make that data accessible with equal ease, and in the same manner, on multiple devices.

What features associated with mobile might migrate back to desktops and laptops? Some are long rumored to be on the way in devices from Apple and other manufacturers: touch screens, gesture-based interfaces, more speech recognition, and so on. The novel constraints on mobile devices mandate their own kind of innovation and shape our experiences; then we expect to be able to replicate those experiences back at our PCs. That forces the traditional forms of those devices to change. “A little four-inch-by-four-inch silver square sits where my mouse used to sit,” says Dahlin, referring to the multitouch gesture pad on Apple laptops.

Not all computer scientists are so sure of the effects mobile technology will have on desktop technology. “My personal perspective is that these are two different things,” says Sanjiv Bhatia, a computer scientist at the University of Missouri-St. Louis. “I cannot do on my iPhone what I want to do on my desktop.” If nothing else, the screen real estate isn’t there. For other obvious reasons—such as lack of disk space and processor power—a desktop device will always be different from a mobile one. Bhatia is also skeptical that the cloud will dominate our lives in the way that others predict. There are too many serious unresolved questions, he says—legal, privacy-related, security-related, and so on.

Bhatia doesn’t deny that some user-experience innovations are likely to trickle over from mobile. “If there’s a good thing developed in mobile OS that solves a problem in desktop, I should use it for sure,” he says. But in terms of underlying architecture and core capabilities, he thinks that the world of the mobile OS will always be stripped down, ersatz.

Barton Miller, a computer scientist at the University of Wisconsin, notes that many PC and mobile OSs are already fundamentally similar. “iOS is really MacOS X inside,” he says, “with layers on top to provide the familiar screen interface and to control the loading and execution of the various apps.” Similarly, he continues, Android is derived from Linux, as are the companies’ other operating systems. The OS groups at various companies “will continue to focus on basic design issues,” he suggests. The end user isn’t likely to feel the effects until design changes reach the higher levels—the user interface. “It’s the layers above [the core OS] that will be the part that is interesting to consumers,” he says.

Of the major software companies contacted for this story—including Apple, Microsoft, and HP—only Google would comment: “Both Chrome OS and Android are innovative open-source projects that are trying to improve the computing experience by approaching the opportunity from different perspectives. At Google we focus on the user and on fostering innovation. Rather than prejudging outcomes, we will continue to focus on users by enhancing choice and innovation in the ecosystem.”

If users do continue to switch devices more frequently and use the cloud more widely, though, then Dahlin’s vision of merging operating systems seems the most likely outcome. “If we do it right,” Dahlin says, speaking for OS designers, “then users shouldn’t have to be sloshing data back and forth between devices or worrying about where things live. That should just happen transparently. Imagine the way you want to think of a physical device: it’s a window on your data, but it’s not your data.”