Microsft said that .NET Core 3.1 will be a small release focused on key improvements in Blazor and Windows desktop. .NET Core 3.1 will be a long term support (LTS) release, and you can expect the final release in December 2019.
Alongside this, the company also announced the release of Visual Studio 16.4 Preview 2, which is also a recommended update to use .NET Core 3.1 Preview 1. As VS 16.4 includes .NET Core 3.1, just updating Visual Studio will give you both releases. According to Microsoft, there are several targeted improvements planned for .NET Core 3.1. You can expect the following improvements in later previews. Till now (i.e. in .NET Core 3.0), the .NET Core Desktop Runtime Installer does not install the .NET Core Runtime. With 3.1 it will be changed so that the Desktop Runtime installer is self-sufficient. The Runtime and Hosting Bundle, for server scenarios, already works this way. C++/CLI was delivered with .NET Core 3.0 release but a developer experience in Visual Studio and the SDK was missing. Microsoft said that it will be delivering that experience with .NET Core 3.1 and Visual Studio 16.4. .NET Core 3.1 will also satisfy macOS 10.15 Catalina’s new security requirement(that applications must be notarized).