From a competition stand point I don't think they can delay the GT500 that long.
The reason Ford generally doesn't released the "halo" version in the first or second year of a new model has to do with emissions/CAFE/crash certification. They have their hands full with all the certifications required on a new platform as it is. This is also why the recent claims of 6 engines being available is also almost certainly false. Too much at one time.