A three year old s85 with 36k miles is around the 55k cpo range so it's about 48 trade in and 51 private sale. And it cost about 95k new before tax rebates. The s90d will prob be similar in 3 years. The D and glass roof and AEP and FSD and unlimited supercharging will bring it higher up cause these are "new" over ap1 and earlier cars. The model 3 will bring it down. Unlimited supercharging if offered for say $2500, then that makes your value bump fixed at that amount. If they build city chargers and don't offer free charging options on new cars then it's a bigger bump up because uber and Lyft or condo and apt ppl would buy your car over new cars. I don't think new S features will affect your value much because it will cost 100k and no tax rebates and that's a diff price league when purchasing. The S is a large car with a huge trunk hatch. So the versatility and space inside may push some to that over a model 3. 7 series vs 5 vs 3. All have a space in the marketplace. So I would say at least 55k.