With the .NET Core 3.0 release in September 2019 we think that
all *new* .NET applications should be based on .NET Core. The primary application types from .NET Framework are supported, and where we did not port something over there is a recommended modern replacement. All future investment in .NET will be in .NET Core. This includes: Runtime, JIT, AOT, GC, BCL (Base Class Library), C#, VB.NET, F#, ASP.NET, Entity Framework, ML.NET, WinForms, WPF and Xamarin.
.NET Framework 4.8 will be the last major version of .NET Framework. If you have existing .NET Framework applications that you are maintaining, there is no need to move these applications to .NET Core. We will continue to both service and
support .NET Framework, which includes bug–, reliability– and security fixes. It will continue to ship with Windows (much of Windows depends on .NET Framework) and we will continue to improve the tooling support for .NET in Visual Studio (Visual Studio is written on .NET Framework).