Boeing (or anyone else for that matter) will not build va successor to Concorde while Concorde is still flying, I suspect. It's all to do with economics.
The most profitable routes for a supersonic airliners, given that nobody wants then flying over land supersonically, are (1) Europe - East Coast States and (2) West Coast States to Japan, with the former being much more profitable than the latter.
The Europe - East Coast route is a money spinner for BA. They have that route sown up, much better than Air France does.
Any aircraft manufacturer would need to spend billions to develop and build a rival to Concorde. Those costs would be passed on to the customers (the airlines) who eventually bought such a machine. The airlines, in turn, would need to pass on those initial purchase costs to their passengers in the form of expensive tickets.
While Concorde is still flying, BA would be able to undercut any fare that any other airline flying a new supersonic aircraft would have to charge, as the BA's Concordes are already bought and paid for and have a much lower cost than any successor would have.
Therefore, whilst Concorde is still flying LHR-JFK and making the profit it does, no new supersonic aircraft will be built, I suspect, due to simple economics.
And as Concorde is planned to fly for another 7 - 10 years, I think we will have to wait a long time for another supersonic passenger aircraft to come into airline service.
Just my view, you understand.
