Thanks for sharing! I'm glad Microsoft is still providing active development for WinForms and on recent .NET Core versions and not just .NET Framework, although the later seems to still be supported indefinitely (for now?). [0]
Oldschool .NET Framework is a Windows component now, so as far as support goes, it is treated the same as any other OS component - meaning that it's supported for as long as the corresponding OS is.
I suspect that .NET will last just as long given the sheer amount of enterprise software that was written for it - even today there are places that target it in lieu of the new OS-independent .NET versions.
How long that will be remains to be seen. But Windows still ships the VB6 runtime (MSVBVM60.DLL) in the box today, 27 years since it was first released: https://learn.microsoft.com/en-us/previous-versions/visualst...
I suspect that .NET will last just as long given the sheer amount of enterprise software that was written for it - even today there are places that target it in lieu of the new OS-independent .NET versions.