I don't know If the Mac App Store will bring better apps and grater for enthousiasm than it is now for Apple Store business model, but you can be sure of one thing : notarisation program will not last. The goal is to lock the platform like iOS and force force every user to get their apps through the App Store and nowhere else.

I'm pretty sur once MacOS has switched to ARM, system partition will be in read only mode, you will not be able to install app outside of the AppStore except if you jailbreak thank to a "security flaw".