People are assuming Apple will allow users to supply their own ROMs, but that’s probably not going to be allowed. This change is probably just to allow game publishers (eg, SEGA) to sell emulated versions of their own games. So not necessarily a big change.
https://arstechnica.com/gadgets/2024/04/apple-now-allows-retro-game-emulators-on-its-app-store-but-with-big-caveats/