I haven't read the new developer documentation, but if it's like the notch of previous years, Apple will recommend that 3rd-party developers don't pay it any heed specifically, and instead rely on the safe area dimensions/constraints provided by the OS in order to control their layouts.

For 3rd party developers to show information in the Island, that will be achieved through the Live Activities API, which is not specific to the iPhone 14 Pro.

The Island will likely stick around for a few years, after which point Apple will adapt that notification area UI to work without the Island.