A quick scan of ebay will show that 13-14 Shelbys can be had for significantly less than when they were new. I'd imagine the GT350 will definitely impact those prices.
Ebay prices are still up there for the 2014 GT500. A $5000 discount is not a big time reduction. Some are still around $67,000. I'm not arguing the point. If someone can get a great deal on a 2013/2014 that would be great, but I don't expect them to sell for $40,000.
2014 Shelby GT500:Delivered 4/3/13, Black/Black stripes/Black interior, SVT Track Package, SVT Performance Package, JLT Oil Seperator, FRPP Resonator Delete, Syntha Max blue air filter, Revan Racing shifter bushing, Michelin PSS tires, Lloyd GT500 mats, and yes the stock Shelby seats.