That's pretty interesting. First we have inverted yield curves on bonds, and now Wranglers!Not according to KBB. Their values show an 18' JK is worth less than a 17' with the same mileage.
For fun I ran the data for the same Sport S with the same mileage as a 13, 14, 15 and 16. The biggest gap was between the 13' and 16' as you'd expect, but the difference was only $1400.
So the reality according to the experts is depreciation between an 18' and 19' is a non issue.