Something To Tide You Over Until Windows XIII
John Cable, the VP of Program Management for Windows Servicing and Delivery released a memo stating the blatantly obvious; a large percentage of the ~1.3 billion monthly active Windows 10 devices out there will not be eligible to run Windows 11. Microsoft seem to have also realized that the last long term servicing branch of Windows 10 was the elderly 2019 version. In order to address the way that their actual customers do business Microsoft have come up with a small concession named Windows 10 21H2, which should not in any way be confused with Windows 10 21H2.
The Windows 10 21H2 you may see in your feature preview is different from the Windows 10 21H2 just announced, as the latter will be the new LTSB version, while the former will be pushed to everyone. This offers an interesting choice for those interested in staying on Windows 10 for the foreseeable future. The 2019 version will have, at least at the moment, a full decade of support and will delay the necessity of adopting a new OS until 2029. The new Windows 10 21H2 will only get five years, so opting for the newer version will mean you have to look at upgrading in 2026.
If Windows licensing has been driving you a bit mad over the past decade or so, it is about to get even more byzantine. That is before you even think about Microsoft 365’s Windows as a Service offerings. There were no changes mentioned on the consumer side, you can still expect to see that version of Windows 10 21H2 supported for either 18 or 30 months, depending on the version you use.
It's a little confusing, because the current preview of Windows 11 also calls itself 21H2. It wouldn't be a Windows update without some attempt to baffle users.