There was a good documentry on the development of Concord and the TUV copy. It ended with NASA buying the last Concordski to use as a test plane for supersonic travel. They wanted to do more experiments, I think in conjunction with Boeing on supersonic jet-liners. That may have been a pre-cursor to the sonic cruiser, as the documentry was on a while ago, but I would not be surprised if nasa and the like continue research.