About a month ago i paid a visit to the Boeing website and their press releases indicate that they still itend to pursue the Sonic Cruiser. Boeing, unlike Airburst, conversed with airlines and airports in order to assess their existing infrastructure and needs and used that "grocery list" as the baseline for the SC. Imagine, asking the customer what they want and what they can handle before you design an aircraft.
That's crazy-talk! What will you want next? To tell the waitress what you would like to eat before she serves you?!? =P