Microsoft is perpetually compiling new builds of Windows 10 for internal use and when one of these builds meets the quality standards for an Insider release, then it is pushed out. While it has been a few weeks since we last received a build for phones, if the telemetry data comes back clean, a build will go out this week.

Gabe Aul, who is head of the Windows Insider program, said on Twitter that if all goes well with build 10080 for phones, then it will be released to Insiders.

@bibeksau You won't :-) 10080 is the current candidate. Pushed to Microsoft ring yesterday. If it fares well, we'll have a build this week. — Gabriel Aul (@ GabeAul ) May 12, 2015

The build is currently being tested by Microsoft employees which is where the telemetry data comes from; Aul and his team are looking for failed installs, major issues that would brick a device and the like. If the data shows that it meets a minimal level of acceptance internally, then it is pushed out to Insiders but the monitoring never stops which is how the team determines if this build makes it to the slow ring as well.

Microsoft has said that the phone builds of Windows 10 are behind that of the desktop which is why the OS will not be released at the same time as the desktop OS. Once Microsoft announces if and when this build will arrive, we will make sure to let you know.