I have been running the exact same trade, except my current driver is a 2015 FFE. My main motivation is to get the updated carpool lane sticker, since that saves me a considerable amount of time on my commute. Here is what I discovered:
1) The lease offer on the Ford website ($149/mo) is misleading. What they don't tell you is that you have to pay sales tax on the $11,000 rebate, which is over $1,000 where I live. The best lease payment my local dealer was able to come up with was almost $300/mo with nothing down, including sales taxes and fees.
2) Availability of the FFE in Southern California is pretty slim, and getting slimmer (in fact, by now, they may all be gone).
3) Residual value, 36 mo / 10K miles, was 32%, or around $9500.
4) The best purchase price I could negotiate was about $3500 off MSRP, before rebates. I'm guessing the discounts may be getting slimmer now that availability is less, but I could be wrong.
5) Since you live in California, remember you will be paying sales tax on the $4000 Ford rebate.
6) Trade-in on my 2015 was about $8000. This was in spite of KBB saying my car had a trade-in value of $12,500.
I also looked at the Bolt. Here in SoCal, the Chevy dealers aren't dealing much on those, at least they weren't about 6 weeks ago. The best lease deal I could get was still in the low $400's per month, and the best purchase price was about $3500 off MSRP, after rebates. The cars you see in the paper with bigger discounts or lower lease payments didn't have the DC charging capability, which I would use if I had it. Chevy isn't offering much in the way of lease rebates (they are keeping the federal tax credit), but they do have a much better residual value (57%). And, personally, I don't really care for the way the Bolt looks, or the interior (not nearly as nice as the FFE).
I decided to continue driving my 2015 FFE. There are going to be a bunch of new EVs hitting the market around the end of the year. I'm particularly interested in the Hyundai Kona / Kia Niro twins. GM is supposed to be launching a couple of new Bolt-based EVs. Figure in about a year I can get some good deals on one of those, assuming I like them.
GONE - 2015 FFE, Magnetic with leather interior, debadged & tinted
38,500 miles (since May 2015), average 246 Wh/mile
REPLACED WITH - 2018 Tesla Model3, LR RWD, Obsidian Black
20,000 miles (since Nov 2018), average 235 Wh/mile