Of the big IPOs expected to occur in 2017, Dropbox’s could be one of the most intriguing.

When Dropbox last raised money, in 2014, it was valued at a hefty $10 billion. But large investors such as Fidelity and T. Rowe Price slashed the value of the Dropbox shares on their books by as much as 50 percent in 2015. The key concern: could a company whose free file storage service is used by hundreds of millions of people find enough paying customers to make a great business?

Investors may be in for a pleasant surprise. According to people familiar with the company’s finances, sales are running at more than $750 million a year, up from around $400 million in 2014. That’s thanks in part to growing sales of Dropbox Business, a souped-up version of the free app that costs $150 per employee per year. The company has been cash-flow positive since early 2016, even as it has made heavy investments in engineering, sales, and IT infrastructure.

Now CEO and cofounder Drew Houston is leading a new strategic charge. In addition to selling utilities to keep digital files safe and accessible, Dropbox intends to offer software that businesspeople use for hours each day to create content and get work done. The company will say more about its product roadmap on January 30, according to an invitation sent to reporters.

“This is a mature, very, very powerful software company,” says Bryan Schreier, a partner with venture capital firm Sequoia Capital, which was an early investor in the company.

That doesn’t mean Dropbox will live up to that heady $10 billion valuation, which even at the time was widely seen as a sign of a bubble about to burst. Even if annualized revenue hits $1 billion by the time Dropbox goes public, investors would still need to think the company is worth 10 times its current sales. These days, the average cloud software company trades at just 4.7 times revenue, according to Bessemer Venture Partners.

Still, Schreier and other investors insist they are no longer worried about Dropbox’s fundamental business model. About 10 million new people start using the free consumer product every month. An increasing percentage of those users sign up for the $100-a-year Pro version, which offers more storage and sharing features. Many of those Pro customers use Dropbox at work, and once their employers realize how popular it is they are more likely to step up to Dropbox Business, which is designed for use by teams rather than individuals. So far more than 200,000 companies have signed up for Dropbox Business, up from 50,000 in 2014. While most are small and medium-sized companies, a few big companies such as Expedia and News Corp. have more than 10,000 seats.

A successful push into productivity and collaboration software could give corporate customers much more to buy from Dropbox. The first example is Paper, which provides a kind of virtual white space where employees and contractors can share Excel spreadsheets, Google Docs, and other digital assets regardless of what device they are using. The idea is to tie together scores of different productivity tools and fold in management tools to help teams keep projects on track. Paper has been in beta since late 2015, but appears to be nearing a general release.

“Paper is going to be really important for us,” says chief operating officer Dennis Woodside, who declined to comment on IPO plans or on the company's revenue. “In five years, you could start a business on Dropbox: that is something we aspire to.”

Dropbox is far from the only company looking to change the way work is done. Google offers G Suite, which contains business versions of apps such as Google Docs and Gmail. Facebook has a collaboration service called Workplace. Microsoft is improving its cloud offerings as it seeks to defend the massive market share earned with its Windows and Office monopolies. Box has strong traction with companies in highly regulated industries like health care and financial services, while younger companies such as Asana, Atlassian, and Slack already handle elements of what Dropbox aims to do. According to Gartner analyst Karen Hobert, there are 130 companies just in the electronic file storage and sync market.

Yet even rivals see Dropbox as a likely survivor of the inevitable consolidation. The overall market opportunity for productivity and collaboration tools is $30 billion, if you replace all those PC disk drives and traditional Windows or Mac programs with cloud-based alternatives. “That’s an order of magnitude more than the combined revenue of all the players today,” says Box chief executive officer Aaron Levie. “As everything moves to the cloud, there’s going to be plenty of opportunity.”

Fending off challenges

Dropbox has been bulking up for this opportunity since 2014, when Houston hired Woodside. A former McKinsey consultant, Woodside joined Google in 2003 as an operations expert, before running U.S. sales and then the Motorola Mobility cell phone division. At Dropbox, he’s hired more than 200 salespeople, up from zero when the company relied solely on Internet clicks. The engineering team has more than doubled to more than 1,000 members, large by any measure. And he has overseen a massive, risky IT overhaul. While most companies are moving more of their business onto public cloud platforms like the one run by Amazon Web Services, Dropbox has shifted billions of its U.S. customers’ files away from Amazon’s platform to three of its own data centers. That way, Dropbox can tweak its network to cut the time it takes to store and sync traffic.

The result is more of a traditional enterprise software company than the hyper-efficient app maker Houston founded in 2007. The idea for the company came when Houston realized during a long bus ride that he’d forgotten the USB drive with his work files at home. The resulting cloud-storage app was a sensation with people who felt his pain. By 2012, Dropbox had 100 million registered users.

Then things got difficult. Giants such as Amazon, Apple, Microsoft, and Google began giving away cloud storage capacity as a way to sweeten other offerings. As prices collapsed, cloud storage specialists faced an existential threat. Even though Box has been farther ahead than Dropbox in focusing on corporate customers’ needs, it still struggled to gain investors’ confidence after going public in early 2015. Until recent weeks, Box shares traded well below the original offer price of $14 per share.

A successful move by Dropbox into the huge productivity and collaboration software market could brighten the outlook, but it will require the company to pull off two tough transformations at once. Dropbox is still evolving from a maker of a free consumer app to a corporate IT infrastructure company. Now it must also move from selling technology that’s designed to be as invisible as possible—after all, people love Dropbox because they don’t have to think about it—to making products people use much of their day. Again, Box provides the cautionary tale. It introduced a Paper-like product three years ago called Box Notes. But Levie admits that its reception has been less than overwhelming. Box plans a “major relaunch” this year.

Woodside responds that few companies have the scale, the technical expertise, and the brand to pull off its ambitious plans. “There’s close to two billion knowledge workers in the world, and I know this much: the tools they’ll be using in five years are not the ones they’re using today,” he says. Companies with huge numbers of loyal customers have a huge leg up in figuring it out, he argues. “Is the number 500 million? A billion? I don’t know. But we have a shot.”