In terms of future collectible, who knows what's gonna happen ?
Some rare cars will never be a sought after collectible and some others will. There are lots of parameters that have to be taken into account.
IMO, the GTS will be a collectible. Why ?
- The GTS timeless shape
- The largest engine ever mounted in a production car (at that time) (as the RT/10 I agree)
- Shelby involvement in development (link with the Cobra)
- It's been a limited production : around 7700 if I'm not wrong. Remember 7177 Ferrari Testarossa have been built (and 2280 512 TR) for instance.
- Most of all, the racing version GTS-R has won most of the best races in the world (Le Mans, Daytona,...)
As for the ACR, even if it will be built in very limited quantity for 2010, available with customised and very rare color combos, will it be enough to make a future collectible ? It's a stunning supercar, but has no race history, and finally the genIV is nothing but an evolution of the genIII, I mean nothing really new out there ! Think about the GTS when it came to the market ! It was a shock !
In other words, go for the GTS.