[Hamuko]

Yeah, I didn't see anything about the Island that seemed to be API-specific to it. Music players will probably get into the Island by just adapting the normal Now Playing APIs that get your media information on the lockscreen, live updates get to the island by adapting the Live Activities API, and so on. Maybe there's some customization that you can do, but I imagine developers don't need to specifically code for it.

And since it's basically baked-in that iPhones will have a front-facing camera, and they don't seem eager to abandon Face ID, I don't see the Island disappearing anytime soon. And even if they get some fancy new tech that allows to hide everything behind the screen without massive compromises, it's still possible for the holepunch design to live on in the non-Pro models and later in the SE models (similar to how Touch ID still exists on the SE).