Microsoft will issue its next Windows 10 upgrade in March 2017, according to clues uncovered by digital detectives.

Tero Alhonen and a Twitter user identified as WalkingCat sussed the likely release timetable from a group policy in the latest Insider preview. According to a screenshot posted by Alhonen, Windows 10 version 1703 will be required for the policy.

Microsoft designates Windows 10 versions with a year+month label. In that convention, 1703 would represent March 2017. Previous versions included 1507 -- July 2015, the debut version -- 1511 and 1607. The last was the most recent, released not in July but on Aug. 2.

Previously, Microsoft acknowledged that it would issue just one Windows 10- upgrade in 2016, but had a pair planned for 2017.

Originally, Microsoft's development-and-release cadence was to be a three-times-annually tempo, or about every four months. Under that regime, an upgrade was to be supported with security updates to commercial customers only until its second successor appeared.

But Microsoft has discarded that scheme. Instead, Microsoft has pledged to support each upgrade -- what it calls a "feature update" -- for a minimum of 18 months. Thus 1507 will be supported until at least January 2017.

Customers can confirm the continuing support for 1507; as recently as last week, Microsoft issued security updates for version 1507.

It's unlikely that Microsoft will actually pull support from 1507 in January. Rather, it would be more reasonable to await the next milestone, 1703, perhaps even extend the upgrade-or-else deadline an additional two months. (Microsoft gives Windows 10 users a 60-day "grace period" at the end of Windows 10 support cycles.)