According to an article in Mashable, NASA's 2019 budget proposal includes funding for a new X-plane, specifically a supersonic aircraft designed to travel faster than the speed of sound without generating a loud sonic boom. Dr. Dimitris Lagoudas, associate vice chancellor for engineering research at Texas A&M University and principal investigator for the project, leads a team of researchers that includes Dr. Rodney Bowersox and Dr. Darren Hartl from the Department of Aerospace Engineering. They are making recommendations to NASA on ways to reduce the massive shockwaves produced during supersonic flight.
The article "NASA believes its supersonic X-Plane will slice our cross-country flight times in half" describes their research that subtly changes the shape of the aircraft in midflight, depending on various weather conditions. If NASA has its way, the first X-plane prototype of this kind will take flight in 2021.