If they can reduce the amount of disturbance reaching the ground to a level that doesn't cause irritation, then supersonic aircraft become a means of pure economics.

In a way, they always were, but the economics were a lot harder when the only flight paths could be other water. Aside from New York-London/New York-Paris, there really weren't any major flight paths where people would conceivably pay the higher required costs.

If suddenly every current airport were opened to supersonic flights, then the economics become quite a bit easier to manager since there are tons of places in general (not just limited to destinations near ocean-crossing flight paths I mean) where the traffic may well see folks willing to pay for supersonic flights if they could.