For the first time ever, Microsoft has started testing a Windows 10 feature update with Insiders well over a year before said update is scheduled to start shipping. Usually, a Windows 10 feature update gets anywhere between six to eight months of Insider testing time, before it's finalized and starts rolling out to the rest of the world. Microsoft's Windows 10 20H1 update, however, is getting a whopping 13 months of testing with Insiders, which led many to believe that Microsoft was planning something big for this release.
This theory was further fuelled by Microsoft's vague reasoning for why 20H1 was going into testing with Insiders so early, stating that some of the things Microsoft is working on for 20H1 require longer development times. While true, it's not as exciting as one might believe. According to ZDNet's Mary Jo Foley, the reason 20H1 has such a long development phase is because the company is planning some significant under the hood changes for its release.
Mary Jo Foley claims that Azure and Windows engineering teams are trying to align with platform work going on internally, and that the work they have planned in this area requires more time than they have for the usual development cycle.
When a version of Windows 10 is being built, platform work (that being work related to the core of the OS) is usually completed a few months before a feature update is finalized. For example, 19H1's platform work was completed in December 2018. In the case for 20H1, Microsoft has some under the hood changes planned that simply wouldn't fit into the normal development cycle for a feature update. As such, 20H1 gets an extra six or seven months of testing so that this platform work can be completed.
What does this mean for 19H2?
Mary Jo Foley states that because of the platform work being done with 20H1, 19H2 will be based on the platform work that 19H1 was also based off, instead of getting its own designated platform work that would've been completed in June of this year as 20H1's platform work won't be completed until December, after 19H2 is finalized. That doesn't necessarily mean 19H2 won't have any new features or notable changes, it just means there won't be any huge platform changes introduced with 19H2, which doesn't mean much for most people.
I too have heard from my own sources that the reason 20H1 is in testing so early is because of under the hood related changes, and not because there's any huge new features planned for 20H1. That doesn't necessarily mean we won't see any huge new features or UI changes, just that the reason 20H1 is in testing with Insiders now isn't related to them if they do show up.
Microsoft focusing on improving the underside of Windows 10 is nothing but good news. It should hopefully mean 20H1's release is more stable and performant than previous ones, something Windows 10 feature updates have been struggling with as of late. The company is taking this kind of thing very seriously, and rightly so.