Comment by dangus

It seems like macOS updates have a lot more to do with underlying hardware and specs than year of release alone.

Going back to the iPhone 5C example, that phone lost updates much earlier than the 5S released the same year because it didn’t support 64-bit processors.

There are also a number of Intel and PowerPC systems that weren’t supported long due to architecture transitions.

I could very easily imagine a future version of macOS only being available on systems that shipped with 16GB of RAM.

Although on the other hand, I think Apple decides on support based on userbase as well. I imagine if they find a device is barely used or don’t sell well in the first place they would perhaps be more likely to drop support.