Terminator!
After the Shelby name is worn out and people realize there are millions of them on the road (been in constant production since 2007), 50 years from now, people will look back at the one that started it all, the 03-04 Cobra, which had a production run of only 2 years.
Of course I bought mine to drive, so I don't really care if it happens or not. But of all the modern Mustang/Cobra cars, the Terminator is the one people will remember once all the hoopla over Shelby dies down. Might have been some cool unique stuff in the past, but now days it's nothing more than a sticker and a PR stunt.
8394 cars isn't exactly rare or low production, but again, it was only a 2 year run compared to the GT500 being carried on year after year after year, and I do honestly think 50 years from now that is going to be a big factor.