Firstly the Branson offering to buy Concorde, dont believe the crap he spouted. Theres alot more to it.
Secondly, Concorde was scrapped because Airbus stopped supporting it for parts because Air France told them they couldn't afford to run the plane any more. It wasn't to do with how old it was or how modern its systems are( some of which are now only just being used in modern jets, thats how advanced it was) BA wanted to continue using it and were starting to make money from it again, but once Airbus pulled the plug on the parts that was it.