It looks like we’re done: Microsoft has pushed Windows 10 Insider Preview build 16299.15 to testers in the Release Preview ring. Pretty much the only milestones left are the public release and the downloadable ISOs.
Microsoft first shipped build 16299.15 to Windows Insiders on the Fast ring exactly one week ago, on October 3. It then shipped it to the Slow ring just two days later.
Since then, it’s been pretty quiet, and many—myself included—have figured that this build, or this build with a cumulative update—would be the final Fall Creators Update release.
With the move to the Release Preview ring, however, this supposition now seems certain. As its name suggests, builds that head to the Release Preview ring are aimed for public release too. This is Microsoft indicating that this build is essentially it.
That said, the way that Windows 10 works is that Microsoft can—and will—update it at any time. So even if build 16299.15 is canonized in ISO form as the final build, anyone who installs the Fall Creators Update will also immediately receive some update via Windows Update too.
Needless to say, Microsoft will almost certainly never say that the Windows 10 Fall Creators Update—or Windows 10 version 1709—is done. But … here we are.