There are commercial reasons for Boeing/Airbus to delay (3) even if the economics for supersonic flight were optimistic, though that didn't stop them rolling dice on the A380/787 as well as plenty of skunkworks projects.

Trouble for Boom is that promising (1) might make raising the capital for (2) more difficult. And also the big risk they deliver (2) which is known to be possible and don't sell enough aircraft to recover their costs.