Ionic 5 was announced a few hours ago (12th Feb 2020) and I upgraded my one of the small production app to Ionic 5 along with Angular 9:
Because of ionic update not fast enough, you can try:
npm i @ionic-native/status-bar@beta @ionic-native/splash-screen@beta @ionic-native/core@beta -S work for me.
update 2020/02/18 => we can run npm i @ionic-native/status-bar @ionic-native/splash-screen @ionic-native/core -S now to get latest stable version