C++/CLIと.NET Core 3の未来 

.NET Core 3.0 is now available and we have received a lot of questions about what that means for the future of C++/CLI. First, we would like to let everyone know that we are committed to supporting C++/CLI for .NET Core to enable easy interop between C++ codebases and .NET technologies such as WPF and Windows Forms.

情報源: The Future of C++/CLI and .NET Core 3 | C++ Team Blog

C++/CLIは.NET Core 3.1/Visual Studio 2019 v16.4以降が対応のターゲットになる。
Visual Studio 2019 16.4 Preview 1で試してみることが出来る。