Re: Trade in value will make it or break it.
a 4 or 5 year old 100K Tesla may prove to be an unwanted relic .
Or a design classic. It's certainly one of the more attractive vehicles out there, and it will almost certainly be seen as the first successful electric car. Beautiful and historically important. IMO more so on both fronts than, say, a mark 1 Porsche 911 or an E-type Jag.
As for advancing battery technology: if batteries in five years time have twice the capacity, surely someone will work out how to retro-fit a better battery into a Tesla? Also a lot of the cost of a battery pack is the raw material (Lithium) it contains. You should get a large trade-in allowance against a new one, and an appropriate payment for the one in a scrapped car.