of course it is all speculation and no one can predict the future, but I would say the 13/14 Shelby gt500's are definitely going to be the most desireable of all the s197 chassis. the top of the line trim/horsepower package for any change in bodystyle/chassis usually is.
as jay leno says regarding future collectability... buy a car that you personally love. that way if it appreciates great, but if it doesn't, at least you still have a car that you love and love to drive.
We'll said :beer: