The short answer: No. Your app will not get rejected.
Apps that's get rejected are usually violating something serious, like consuming to much CPU, calling Apples private APIs, responding to user input in an unpredictable manner or simply crashing etc - not just code design issues.
It sounds however like you should consider moving your model some place else, for the sake of ease the maintenance of your code.
Consider creating a modelClass that implements the Singleton pattern. The purpose and responsibility of the AppDelegate should be limited to starting up your app and controlling its lifecycle