I read today some speculation that the 2014 model will be the new design in order to time it with the 50th anniversary. Maybe an extended run of 13's so they can call the new model a 2014 1/2 ?
I have a feeling Ford set up the early production for a reason. MY 13 in winter/spring 12, MY 14 in winter/spring 13, and MY 15(redesign) for April/May 2014. Very much like the 64 1/2 debut in the summer of 64.
Shelby (as in SAI) doesn't have anything to do with the current GT500.