IMO, the 2020 is going to be the worst year to buy because GM was using up all of the leftover stuff to build them, while getting an extra year out of the K2 platform. I'm sure the 2020 LS and LT will see big discounts to move them off the lots so they can sell the T1 platform. I'm sure they will try and still get TOP dollar out of the Premium and RST models to offset the discounts on the lower trims. The 2015-19 will probably stay about the same value, it seems no matter if you have a GMT, or K2, the value stays hi for many years to come.