So earlier this year Microsoft (MS) ended the development of the .Net Framework package. The final version will be 4.8. What this means is that going forward only security patches will be made, no bug fixes and certainly no more enhancements. Instead, app developers are encouraged to switch to .Net Core.
One issue with this is that there is no path for WebForms apps to .Net Core. It’s a complete rewrite. Even for MVC applications the effort is significant, the effort for WebForms is massive. Many thousands of these applications exist – I presently work on one – and they mostly serve a critical purpose in business and most don’t have the budget to rewrite them.
So most of these apps will remain and be bug fixed and possibly even extended.
I understand the reasons that MS did not bring over WebForms because it was very wired into IIS and MS wanted a platform that worked on all plaforms. And I don’t know 100% the technical reasons why something could not be made to simulate or replicate the functionality in .Net Core. I’ll never know.
In the meantime .Net Framework is built in to Windows 10 and will all be around. Much of Windows 10 depends on it. So don’t worry, your apps will carry on running and there are still devs around that can work on it (I am one of them).
And should you feel like putting your app on the Cloud this chap shows some interesting possibilities. https://channel9.msdn.com/Events/dotnetConf/Focus-on-Microservices/Evolving-NET-Framework-Monoliths-with-NET-5-and-Kubernetes