We're not quite here yet. I think a better version of Gatekeeper would offer:

      Only those from Trusted Sources
      Only those from Trusted Sources or which are signed by a developer ID
      Any app, whether signed or unsigned

Where "trusted sources" is something that future Gatekeeper would give you control over.

Enterprises spend a ridiculous amount of effort in locking down and pushing out software to workstations, so allowing them to maintain their own code-signed internal "app store" could be game changing. Apple has almost no enterprise presence, and this could be an opportunity for them to steal market share from Microsoft, who lately appears directionless and out of touch.