Back on topic..
I think the trick in being able to do this automatically will be for Traktor to know the difference between a track being cue'd and a track being played.
Right now my history lists contain the tracks I've cued up and changed my mind about playing. There was some talk about an upcoming version of Traktor having the ability to set a threshold of some sort to determine if a track has been played or not. Also, what about short loops?