> We do not guarantee 100% compatibility between major versions. This is true for both ASP.NET Core and the runtime itself. We intentionally make breaking changes where we believe that they are necessary to move the platform forward and the cost of the .NET ecosystem adjusting to them is low enough.
There is a major .NET release every year. Every other release is LTS with 3 years of support.
> The old .NET framework will be supported for many decades into the future
I'd guess so but Microsoft is not as clear on this as you'd wish. In all their policy documents they say it's "supported as a Windows component on the latest required update" or "Beginning with version 4.5.2 and later, .NET Framework is defined as a component of the Windows operating system (OS). Components receive the same support as their parent products, therefore, .NET Framework 4.5.2 and later follows the lifecycle policy of the underlying Windows OS on which it is installed." To me this seems to be carefully written to allow the possibility of changing that Windows component status in a Windows release. So, .NET Framework is supported as long as it is part of Windows, until it isn't.