There's a good reason why it still takes hours to fly cross-country: supersonic airplanes are still so noisy that it's utterly impractical to fly them over populated areas. That's why the Concorde was largely relegated to overseas flights, after all. However, NASA has a new sensor that could usher in an era of quieter supersonic aircraft. The Eagle Aero Probe (the device you see in the red housing above) measures air pressure changes right near where they occur during a sonic boom, giving a near-instantaneous sense of what's happening. Previously, the sensors were about 15 feet away in the radar dome -- not exactly helpful when you need real-time data to measure a shockwave.
It'll be a long while before the probe enters full service. Right now, the focus is on testing aboard NASA's own F-15 Eagle aircraft. Provided it does make the grade, though, it could be extremely useful for studying the aerodynamics of new aircraft and reducing the loudness of their sonic booms. Eventually, you could see a wide range of supersonic aircraft that are relatively silent, including passenger jets -- your New York-to-LA flight wouldn't have to chew up a large part of the day.