If commercial supersonic flight has any hope of being economically viable, one of the prerequisites will be cruising below Mach 2.
[1] https://news.ycombinator.com/item?id=27386119
[2] https://news.ycombinator.com/item?id=35124271
[3] https://news.ycombinator.com/item?id=35126733
Relative to say Concorde, acquisition costs and direct operating costs need to decrease and # of revenue-generating flights/time need to increase for viability. All of these point to slower speeds. If the perceived boom noise of the "quiet" supersonic designs is low enough, supersonic overland flight could potentially be permitted (NASA is trying to make this possible via this X-plane), with vastly more addressible market. Low boom limits the Mach number.