Would there be a significant time-saving advantage over the current process?
With a short cut key, you'd still have to highlight the track header in order to apply a short cut key. Then you'd have to hit the Ctrl button along with another button. Currently, all you have to do is highlight the track, the back button and then select 'duplicate track'. To my mind, each process would take about the same time with around the same number of keystrokes.
If it is not for copying existing tracks already with media in it but creating a certain number of empty tracks: There are several scripts already which do this.