The WIN10 anniversary edition will feature “Limited Periodic Scanning” which will allow the MS Defender AV product to perform additional secondary checks to complement the product’s main AV defense system.  For example a user with McAfee or Norton AV protection can implement the “Limited Periodic Scanning” capability and this will be performed during a less active timeframe for user to reduce performance degradations.

https://blogs.technet.microsoft.com/mmpc/2016/05/26/limited-periodic-scanning-in-windows-10-to-provide-additional-malware-protection/

Windows 10 is the most secure operating system Microsoft has ever shipped, and we continue to make it better with regular security updates and new features. For example, we’re making malware detection and protection even easier and more seamless for our customers, whether they choose to use the built-in Windows Defender antivirus or a third-party antivirus solution. Starting with the Windows 10 Anniversary Update this summer—and available in this week’s Windows Insider build—Windows 10 will include a new security setting called Limited Periodic Scanning.

When enabled, Windows 10 will use the Windows Defender scanning engine to periodically scan your PC for threats and remediate them.  These periodic scans will utilize Automatic Maintenance—to ensure the system chooses optimal times based on minimal impact to the user, PC performance, and energy efficiency—or customers can schedule these scans. Limited Periodic Scanning is intended to offer an additional line of defense to your existing antivirus program’s real-time protection.