Today, Microsoft announced a new Windows Server Insider Preview build, as well as its second Technical Preview of Project Honolulu. The company also quietly released a new SDK Insider Preview for build 17035.
There's been no official announcement for this just yet, so there's no changelog to report on. Presumably, it includes updated APIs to coincide with the newer build.
It's the second SDK Preview for the Redstone 4 development branch, the first being build 17025. It's only formally supported on Visual Studio 2017, so you shouldn't use it with earlier versions of the IDE. It's also not recommended that you use it in a production environment, although you should be able to install it and still submit your apps to the Store, as long as you target a non-preview version of Windows 10.
It's also worth noting that with build 17025, there was a known issue that caused installation of the SDK to fail on production versions of Windows 10, so until we can see the release notes of build 17035, you might want to stick to a Windows 10 Insider Preview machine.
You can download Windows 10 SDK Insider Preview build 17035 from the Insider page here.