Microsoft tests Windows 10 builds through the Windows Insider Program, which allows users to test new features early. The main branch of the Insider Program focuses on the next Windows 10 build, but Microsoft is now testing Windows 10 20H1, which is over a year away from being launched.
Under the testing model, Microsoft previews the next update, which at the moment is Windows 10 19H1. However, the company also has the Skip Ahead branch, which so far has focused on the next update in line, which would be Windows 10 19H2.
Microsoft would not be expected to start previewing Windows 10 20H1 on Skip Ahead until after the launch of 19H1. However, the company is out of the gates early and a report from ZDNet suggests several reasons for the decision.
Leading the way is Microsoft's continued alignment of its Azure and Windows release schedule. Windows OS engineers have been under the Azure business since a reorganization last year. Under the Azure umbrella, Windows engineers are like to deliver updates to match the priority of the Azure team.
That means realigning when Windows 10 updates are surfaced. At the moment, Microsoft releases an update in April (April 2018 Update, Creators Update, etc.) and another in October (October 2018 Update, Fall Creators Update). However, to move in line with Azure, a June and December schedule will be adopted.
Windows 10 19H1 is arriving too soon to make this change, but the second Windows feature update of 2019 will likely arrive in December. That also means Windows 10 20H1 will now land in April 2020, but instead in June.
It is worth noting Microsoft has not confirmed this reconfiguration, but it seems likely that is what is happening.