This sounds so dystopic. I hope that being able to publish software without having to bow to a gatekeeper won't become a thing of the past.
And if iOS Safari (Apple's "gatekeeper" of last resort) falls too far behind, I'll take myself and the whole gang I serve as "IT installer, fixer, and advisor" for right out of Apple land.
As Mojave is getting iOS security model, Windows is merging the Win32 into UWP, ChromeOS and Android are turning into one OS, and who knows what they would do with Fucshia.
macOS is getting a new security runtime, the scope of Gatekeeper will be expanded, entitlements will be required for all security critical OS areas, application signing and registration even for apps distributed outside the store.
For Mojave, it will still be opt-in, later versions depends on how it will received.
"Your Apps and the Future of macOS Security"