It doesn't have "a worth" at this point. The trade in value against a Z is situational, and varies with the dealer, his stock and his ability to move your trade-in quickly. It's the dead season now, and many dealers are really loaded with C7s, including Zs. Corvette Conti and others are dealing to move out stock, and this may be a good time to dicker. They can always move your 2014 easier than a hundred grand Z, even in Winter.
I'd advise you to go shopping. There have to be dealers out there that would deal on an in-stock Z, especially if they have a dozen or more coming in before the Spring thaw. It doesn't cost anything to contact the by email or phone before the selling season starts.