The US military is working on adaptive engine technology that they claim will be as big a jump as going from turbojet to turbofan.
"Advent and AETD are developing and maturing technology for engines with a “three stream” architecture. In addition to the high-pressure core and lower-pressure bypass streams of a conventional turbofan there is a third, outer flowpath that can be opened and closed. For takeoff, the third stream is closed off to reduce the bypass ratio and route more of the airflow through the core to increase thrust. In cruise, the third stream is opened to increase the bypass ratio and reduce fuel consumption."
Although fighter jets obviously can take greater advantage of this than airliners because of their wider operational range, they claim a potential 35% SFC reduction for transport aircraft too.
Is there anything like this going on for airline engine research?