In order to answer the original question of how much more they can depreciate, it's important to understand why they're depreciating at such a high rate. The short of it is product education. As long as people remain ignorant to the actual needs and continue insisting on 200mi range EV's because anything less is garbage next to a Tesla Model 3, there will be little demand for low range EV's like the i3.
WHY THE DEPRECIATION IS HAPPENING: (Deep breath. This is going to be a long one)
1. The i3 is overpriced to start with. The uniqueness of the car has a premium. Any and everyone who steps into one thinks, "I like this, but what? This is a $50k car?" So the used prices is just getting back to reality of the actual market value of the car.
2. EV's in general are a new technology (not really, but you know what I mean). People were scared to buy them b/c they didn't really know what to expect and b/c they recognized that battery technology was improving so quickly. So this answers one of your questions about why anyone would buy a new one. The answer is that people don't buy new ones. They either buy used ones or lease new ones with good reason.
3. The Tesla brand brought to attention EV's to more people than who otherwise would've been interested in EV's. It brings people who really have no business driving one at all. The 100mi range number is arbitrary and it keeps growing. People now want 200mi ranges. The first question a newb asks after learning you got an EV is, "What's the range on it?" Low number in their head is bad and high number is good w/o any sort of reasoning. Toyota, BMW and DOT did studies about "average" commutes, came up with different numbers and designed their car's ranges accordingly. People are looking to only charge their EV's as often as they get gas at a gas station. This is ludicrous thinking, but it's true. So as long as the ignorance of their actual needs continue to grow and they don't recognize that their EV range doesn't need to exceed their daily out and back commute + errands needs, longer range will always be better. Most people don't see that with 10% left on their battery, they're still carrying 100% of the weight of a battery. It gets less efficient as the battery gets depleted. To sum it up, as long as people want larger and larger batteries with longer ranges without recognizing the drawbacks like cost of replacing the system, time it takes to charge a larger battery, slower, etc, the low range EV's will relatively be viewed as even lower and seen as garbage.
Luckily this is the case, b/c there's people like us who find the i3's range is perfect whether it be the BEV or the REV and understand exactly what we're getting into and why we didn't buy the other cars. So no need to complain. Just embrace their ignorance of the "other side" and realize this translates to a huge opportunity for us to pick up these cars for cheap.
4. The hot girl effect.
Mercedes suffers from this too. That was my last car. I bought it 3rd hand from the person who got it as a CPO car. He paid 32k. Not sure what the original MSRP was, but I paid $18,200 with 55k miles on it and it was only 2 years old. Mercedes has the second worst resale value of any luxury vehicle (behind Jaguar). The hot girl effect is like how people think the hot girl is always taken and "must have a boyfriend". If enough people think that, then no one goes after them and that's why a lot of them are actually single. People also think hot girls are high maintenance. They don't always. So b/c of these misconceptions, what's seen as a highly desirable girl becomes only that. No one actually pursues them and they remain single.
No one is pursuing the BMW i3 for the same reason. it's seen as too expensive. With a $50k price tag, how much can they actually drop? As a BMW, doesn't it have a high maintenance cost? The public thinks that the i3 is too pricey to buy and too pricey to maintain, so they avoid it and buy stuff that is safer and more attainable, leaving the i3 to be less pricey and overly attainable.
Another example is the fast lane on the freeway. Everyone wants to go in the fast lane to go faster. At a certain point, there are so many people in the fast lane that it becomes the slow lane. It gets all the attention while the actual fast lane is the third lane over. People's actions, right or wrong have the power to change the conditions. We'll see examples of that to follow.
WHAT'S IN STORE FOR THE FUTURE FOR DEPRECIATION?
I was at the dealer 3 weeks ago and saw a 2018 MSRP for $61k. Later this year, BMW is supposed to release an even longer range battery. Not the 94ah one, but the even larger one. Not released yet (in the USA at least). There will be a point where the public will say no to the i3. It's not like BMW can charge $75k for this new one that's supposed to be released. Imagine a 2019 (out in late 2018) i3s REX for $75k. It's not going to happen. $65k maybe. But the point is that the potential buyers will no longer become buyers at a certain price level. BMW will have no choice but to extend the savings of battery prices as they get cheaper and cheaper to the public in the form of a car not priced at the same increase in tier as the versions that came before it.
As long as prices get higher and demand for high range EV's continue on the rise, there will be more and more leases and fewer and fewer finances of these cars. More leases means more inventory when the leases end.
So the question is will we see another influx of inventory from lease returns. Highly likely, but at the same time, confidence in EV's is growing from consumers. Remember that people are leasing b/c of low confidence in reliability and concern about higher range vehicles in the future that they don't want to miss out on. There will be a range cap too. I still think 200mi is crazy, but it doesn't mean it can't get crazier. Once SF people can go to LA on a single charge and back, that's the absolute limit. Haha. When consumers find their sweet spot, they won't know it. But once they do realize it, that's when depreciation will stop freefalling.
My guess is that the sweet spot will be like the new Nissan Leaf. Consumers will want a 150mi range car and won't want to pay for a battery that gets them any further. When that hits, whatever the price is for sub 100mi range cars will be what it is. No more tapering off.
A fanatic of all things electric. Ridables like electric ice chests and stand up scooters I adore. Drones like DJI, I root for. I'm a fan of both, but nothing beats my love for my 2016 i3 Rex with Deka World. Shhh, don't tell my wife.