Mach 1.2-1.5 has huge transonic drag and the massive additional fuel consumption will eat away you range, which is not worth the marginal overall speed increase.
Aerion AS2 will be the first production aircraft to employ a
Supersonic Natural Laminar Flow wing, after apparently successful tests with NASA demonstrating an SNLF airfoil at high Reynold numbers suitable for a commercial jet.
A laminar flow wing significantly reduces drag, up to 90% reduction compared to current supersonic wings. The reduction in total drag (including other parts of the aircraft) is more modest -- predicted to be around 20% -- but that's enough to make supersonic flight economical.
Aerion's airfoil was able to simultaneously maintain laminar flow while shaping the sonic boom to enable quiet flight.