Microsoft today released a new Windows 10 SDK Preview build, 15021. There's no actual corresponding Windows 10 build, but the company did release 15025 for PC and Mobile this week, and 15023 for Xbox One.
Here's what's new:
This Windows SDK includes updates and additions to the Windows namespace. See section API Updates and Additions below for the list of differences since the Windows 10 Anniversary Update (Build 10586)
Unlike the last SDK Preview build that was released, 15003, there are no known issues listed. This means that there should be emulators included, and you should be able to set 15021 as the SDK version when creating a new project.
There are a number of API changes, which are far too much to list here. You can find them at the Windows Blog post.
As usual, you should be using a Windows 10 build that corresponds with the SDK build number or greater (15021 or better), so you'll need the latest build on whatever platform you're developing for. The other prerequisite is that you'll need to be running Visual Studio 2017.