You are largley right here, the gains in thoughput in the system will be made by reducing seperation between aircraft, so you can have twice as many aircraft on the same airways. Those reductions in seperation can only go so far, as you have to have a system that can still fail back to stone age (100% down) and still be reasonably safe. At that point controllers fall back to using primary radar, radio and bits of paper in stacks, i.e. how it used to be done before computers.
The improved processing and tracking allows some saftey margins to be compressed, but not many, and not by much.