Turbofans are not exotic technologies. They are well understood, and their limitations are well understood.
Presumably, an SR-71 successor would use a mix of turbofans and ramjet/scramjet to meet their performance (speed/altitude) goals, depending on whether it would be self-sufficient or use takeoff assist from another aircraft.
Presumably, an SR-71 successor would use a mix of turbofans and ramjet/scramjet to meet their performance (speed/altitude) goals, depending on whether it would be self-sufficient or use takeoff assist from another aircraft.