With Windows 10 20H2 done and starting to roll out to users, everyone wants to know what’s next. Based on recent patterns, it should be Windows 10 21H1 — the “spring” feature update for Windows 10, followed by an incremental 21H2 “fall” feature update. But the arrival of Windows 10X is going to shift the Windows landscape in 2021.

While it was housed in the Azure organization, the Windows engineering team was following the Azure “semester” development schedule, with new features assigned to either the January to June bucket or the June to December bucket. The June to December 2020 bucket is codenamed “Iron” and the January to June 2021 bucket is “Cobalt.”  Features that fall into any given semester bucket can roll out in any Windows 10 release; they are not necessarily tied to the release when they’re ‘built.’ And Windows 10 feature updates that include features largely built during a particular semester are known by those codenames.

As I previously reported, Microsoft might opt to skip releasing a 21H1 Windows 10 feature update. (Officials won’t confirm or deny this every time I ask.) Instead, they might just do one feature update next year, the “Cobalt” update in the fall of 21H2. In the spring, last I heard, Microsoft is planning to release the first iteration of Windows 10X — its simpler and more secure Windows 10 variant which it originally planned to debut on dual-screen devices, but now plan to roll out first on new single-screen PCs and 2-in-1s.

Today, October 28, Windows Central reported that the 21H2 Cobalt Windows 10 feature update isn’t going to be minor. It’s going to be much bigger than the usual feature update and will include a UI refresh across a number of Windows components and apps. The UI refresh itself is codenamed “Sun Valley,” according to Windows Central’s Zac Bowden. This UI refresh will include an overhaul to the Start Menu, Action Center and some in-box/bundled Microsoft apps, Bowden says, and will be an optional change.

My contacts say the Sun Valley codename does, indeed, exist. According to materials from this summer that I’ve seen, Microsoft engineering has been describing the version of Windows 10 due next fall as “Windows 10++.” So perhaps Sun Valley is the equivalent of the “++” here. These ++/Sun Valley changes also are likely to work their way into Windows 10X for single-screen devices by Spring 2022, based on the last information I’ve heard/seen.

I’ve asked Microsoft again today if it is changing how it will be rolling out new features to Windows 10 users starting next year. I can’t help but wonder if Microsoft will add some new Windows 10 features via Cumulative Updates up until the fall 2021 Cobalt feature release. If and when I hear more from Microsoft, I’ll add the information to this post.