Today, Windows developer platform head Kevin Gallo was live on Channel 9 for a Windows Community Standup to discuss the software development kit (SDK) for the Fall Creators Update. During the webcast, he announced that the SDK is now 'platform-complete'.
This means that all of the features coming in the next feature update to Windows 10 are already included in the SDK. From here on out, the remaining SDK Preview builds will include mostly bug fixes.
The SDK Preview build that Gallo was referring to is 16232, which was actually released back on July 12, and you can download it from Microsoft here, as long as you're a registered Insider. It's only officially supported by Visual Studio 2017, and while you can run it in a production environment, you still can't submit apps that are targeted at the Fall Creators Update to the Windows Store.
Unfortunately, a feature that is still missing is the ability to compile a UWP app in ARM64, which is interesting given that Windows on ARM PCs are right around the corner.