[pitterpatter]

No, once 20H1 was released it got cut into its own release branch. 20H2, 21H1 and 21H2 are all just updates on top of that branch. You can tell because their build numbers are all 1904x.

Windows 11 is based on the mainline branch after the above (though it too has been cut into its own release branch now). of course, some changes might be ported back and forth between releases.

So machines not eligible to be upgraded to Windows 11 will stay on Windows 10 and get 21H2 and who knows how many more updates.