With just over two weeks to go before it releases the one-year anniversary update to the Windows 10 operating system, Microsoft has acknowledged that it doesn't expect to meet its goal of 1 billion users by 2018.

The changes in the company's phone business means "it will take longer than FY18 for us to reach our goal of 1 billion monthly active devices," Yusuf Mehdi, corporate vice president for Microsoft's Windows and Devices Group, said in a statement. In the spring, Microsoft announced that it would sell its feature phone business, and also reported a double-digit decline in Windows Phone sales.

According to Microsoft's most recent update, Windows 10 is now installed on more than 350 million devices worldwide. Downloading the update has been free for users since it was released late last July, but that's set to change with the Anniversary Update scheduled for August 2.

Monthly Enterprise Fee Starts Soon

Mehdi revealed Microsoft's changing expectations for Windows 10 adoption while speaking with ZDNet last week. Before Windows 10 was released last summer, Microsoft executive Terry Myerson predicted that there would be 1 billion devices running Windows 10 within two to three years of its release.

Until now, users have been able to upgrade to Windows 10 at no cost. After July 29, however, enterprise Relevant Products/Services users who have not yet downloaded the new OS will be charged a monthly subscription fee of $7 per seat per month, Mehdi noted in a blog post last week.

More than 96 percent of business users are already running active pilots of Windows 10, he added. According to a recent Forrester Research study commissioned by Microsoft, enterprise adopters of Windows 10 are seeing their deployments pay off in just 13 months.

Anniversary Update Boosts Security

The Windows 10 Anniversary Update is set to bring a number of new features to the cloud Relevant Products/Services-based operating system, including more capabilities for Microsoft's artificial intelligence assistant Cortana and updated biometric security features via the Edge browser. Edge, which rolled out with Windows 10, replaces Microsoft's previous browser, Internet Explorer.

Two new security features for enterprise users will also be released on August 2: Windows Defender Advanced Threat Protection and Windows Information Protection. These tools are designed to help business users better detect, investigate and respond to attacks on their systems, Microsoft said.

"In most instances, organizations are moving quickly to Windows 10 due to the heightened security risks they face and the industry-leading security features in Windows 10 that can help protect them," Mehdi said in his blog post. "Companies of all sizes face real security threats from sophisticated hackers and cyber-terrorists, costing an average of $12 million an incident."

In the U.S. alone there are more than 56 million small to mid-size businesses in critical sectors, such as healthcare, legal and financial services, that need strong security similar to what Microsoft's large enterprise customers get through volume licensing agreements, he added.

Other new features coming out with the Anniversary Update include Windows Ink, a digital pen application that enables users to write on their devices as they would on paper; power-saving improvements for Edge; and new features for gaming.