The Sonic Cruiser is not the answer to Boeing's woes. For some reason, they still insist that airports are not congested, that the system is not creaking close to capacity, and that more frequency is what the public want.
How can they be serious? Some of the worst taxiway queues are in the US hub airports. I have sat on the taxiway rolling an aircraft-length forward every 90 seconds for 45 minutes at Minneapolis, Charlotte, Newark, Altanta. And every city-pair I can think of has ample frequency - there is daily non-stop service or more from London to the likes of Baltimore, Phoenix, Raleigh, San Diego, Charlotte, Cleveland (hardly in the league of NY / LA / SF / Chicago) in the US, five times a day from London to Sydney... There are regional jets which fly all over Europe from the likes of Southampton, all over the US from the likes of Elko NV, Ottawa, San Jose CA... Is there really a city-pair in the world which does not offer ample options should the meeting end two hours early or half a day late?
For my money, Boeing lost it with the 737 "NG". When they needed to come through with something to compete with the A320 and maybe begin a line of aircraft with common type ratings, they instead did very little. Look at the overhead panel on a 737-100 and a 737NG. 35 years in the making? Oh dear.
Regarding Concorde, this lovely aircraft was doomed fairly early on. The British were screwed by the French over a joint-venture missile development and therefore the penalties for either side to walk away from Concorde made cancelling the project very difficult, even though both sides had their doubts. Braniff were very keen but they looked at a cabin mock up and the actual operational stats and told the consortium, "It's too small, it's too slow, it's range is too short." Lufthansa were interested as well but Concorde does not have the range for Frankfurt to JFK.