A $100k, 36 month old Tesla with 45k miles will have a guarantee resale of about $48k. At this rate it would be worth $30-34k at 48 months and 60k miles.
In comparison I just traded in my $29k, 48 month old Toyota Highlander with 80k miles and I got $19k.
It seems like the bar is set pretty low with the trade in guarantee. There are a couple of additional costs as well:
Service plan is for 4 years. As a result most will just pay for the $600 annual service, results in an additional cost of about $375.
An additional 1% on an $80k loan will cost an additional $2-2.5k or so after 3 years.
I'm pretty confident my Tesla will still be worth more than $29-32k after 4 years, so I am financing elsewhere.
Tesla it's trying to avoid the haggling you see at a traditional dealership, which is nice, but I don't think Tesla is going to have used car lots, so the trade ins will probably end up with AutoNation or something similar. This will lead to a price structure for trades below what the car is worth at auction.