Some of those details are still in flux and under active development with the SwiftUI folks. But the initial thought is that all @*Object property wrappers will be able to be used as their non-object counterparts - i.e. where you used @StateObject before just @State etc.
Obviously since that is still under development to see if that works or not I don't have precise details on exactly how that will pan out. But the intent is to allow for when Observable is used developers need to consider fewer potential property wrappers and in the case where no lifetime specialities or bindings are needed and just plain observations are desired, no property wrapper is required.
The take-away here is that the observability portions will all be part of a cross platform and open package/addition (depending on where the homing puts it). So hopefully some of that magic can be dispelled a bit to a simple interface.