I am sure a Concorde could be made airworthy for a one off ferry flight if required, it would entail the robbery of parts from the other airframes and many concessions to life expired parts, but as for semi commercial/airshow use its a complete and utter NEVER.
I personally know of components that were causing real maintenance problems while the type was still in service, let alone after these years of inactivity.
It was only the determination of BA/AF and their subcontractors that just about kept it going to the end.
Since then the expertise, knowledge, spares, test equipment, authorisations, facilities have all been lost. It cannot be brought back.