I don’t think notarization is the issue - I believe it’s going to be natural transition for ARM-translated Mac apps to be MAS-only, and for the sake of security and device management (and profit) Apple is going to follow the well-worn path of iOS and make ARM-based Macs App Store-only.
Because that’s going to be a tough sell for some, that’s one reason I believe we’re going to end up seeing a line of dual-boot ARM-based Mac laptops introduced right off the bat that run iOS alongside macOS, probably with small OS tweaks/nods to the touchscreen on the Mac side for scrolling and selecting, and greater trackpad support in iOS.