If you are referring to the ST170 then they will never go up in value or ever be considered a desireable classic. Not fast enough, too expensive to run (insurance, tax, fuel) too many unique parts that commonly and regularly go wrong and are expensive to replace and they will always be massively overshadowed by the RS because of the humongous performance and desirability gap between those models. The Fiesta ST is the top performance version of its model so has a far better chance of becoming a future classic.

IMO