Microsoft released Windows 10 SDK Preview build 18272, which you can now download from the Microsoft server. This is the first SDK preview build released for the 19H1 development branch, meaning that it's for the next feature update for the OS.
Here you can download the latest preview build of Windows 10 Software Development Kit (SDK). You must be an Windows Insider to access this.
While Microsoft is working on the new 19H1 feature branch of Windows 10, targeted to be release in April 2019, Microsoft now released the first preview build of the Windows 10 Software Development Kit (SDK) to help developers start building apps for the next feature release of Windows 10.
The latest SDK preview build does not include any new major features, but a list of API updates are available in this build. This also includes few bug fixes. Going forward, it should offer new APIs that correspond to the new features in the next version of Windows 10.
If you want to check out the new SDK, you can find it here, under the developer section on Windows Insider. You must be an Windows Insider to access this.
Windows 10 SDK Preview Build 18272 can be installed on latest version on Windows Insiders Preview in conjunction with the previously released Windows 10 SDKs and Visual Studio 2017. In case you need, here you can download the latest version of Visual Studio 2017.