While we're only a couple of weeks removed from the latest Windows 10 release, Microsoft is in full developer support mode and offering Windows developers looking to get a leg up on app features access to the next releases SDK.
During Build 2018, Microsoft executives talked about several application features that will be enabled in future functions of Windows and their selling that functionality against what has been released just today, known as Redstone 5 SDK.
Redstone 5 is the codename for the next release of Windows 10 and the new SDK (build 17661) for developers has been seeded for developers who are part of the Windows Insider program.
Based on what was mentioned during the first keynote at Build 2018, the 17661 SDK will have support for enhancements to the new Microsoft Fluent design language for not only UWP apps but those of Win32 creation, Visual Studio IntelliCode, a new product called Project Kinect, Speech and IoT Device SDKs and further HoloLens integration.
The detailed notes that usually accompany SDK releases have yet to be posted, and most likely won't show up until after the new guy in charge of part of Windows development, Joe Belfiore speaks a bit a length about new upcoming features, sometime tomorrow.
However, if you want to get started testing out new stuff in Redstone5, you can download the new build here.