That requires sufficient interest for people to come up with a perfect emulator for the system before the original hardware becomes too inconvenient to use for

That requires sufficient interest for people to come up with a perfect emulator for the system before the original hardware becomes too inconvenient to use for reference. And that can take a while - Dolphin only just became able to run all GC games a few months ago, for example, and it still has inaccuracies.