I thought i was fairly clear on that point, even in the part you quoted. We're talking a used MS, not necessarily a 4 or 5 year old one, just one that fits in with the high end Model 3 market. so what will next year's model S look like? (it will be 3 years old by 2018, and honestly, I think anyone who expects the model 3 to be available in 2018 is deluding themselves based on Tesla's track record with timelines)
Point is, we know a NEW model S will be better than a NEW model 3, and therefore a USED MS that's the same age as a USED Model 3 will be better as well. What we can't say is where the crossover point is, 1 year? 2 years? 5? 10?
Also, as I pointed out, we don't know what "better" really means anyway, there will be different things important to different people.
@joer00 Do you think a 2010 MS, fully loaded, is worth less than a 2014 MS, also fully loaded? (keep in mind that "fully loaded" now includes several features that did not exist before, such as parking sensors, folding mirrors, etc)
Now extrapolate that further, imagine the 2016 MS that has full self-driving capability (Elon has already promissed on-ramp to off-ramp by end of this year, so the hardware will likely be there, the rest is free software updats), is that worth more than the 2014 MS that doesn't have that hardware?
Now justify why your used car shouldn't depreciate when it's missing many of the features of the new car, has less of that warranty remaining, has more wear and tear on the seats, paint, dash, etc.
As you pointed out, supply and demand drives prices, when there's supply of better cars than yours out there, people won't demand yours over the better ones unless your price is also better. It's obvious you don't want to sell right now, so you are over-valuing your car, wait until it's time for you to want an upgrade, and then see what you think.
