First, to the OP...
No one outside of Tesla even knows what the production Model 3 interior will look. So we'll have to wait on that.
As for tax credit availability... it's a crap shoot. Did you get your M3 reservation in person before the unveiling event? That would give you a big leg up, and being in CA would help too. But there are so many unknowns still about how Model 3 production and delivery timelines will play out.
As for depreciation, it's been pretty awful for almost all new EV's -- with the exception of Tesla. However, you're right that the huge numbers of M3's that Tesla hopes to build could completely change that dynamic. So a used vehicle would definitely help insulate you from that.
It's hard to go wrong with a Volt. I like mine a lot. I'd probably have upgraded to a Gen 2 Volt if the Model 3 wasn't right around the corner. Also, you might consider a used Gen 2 Volt instead of a used Gen 1 if you don't mind paying more. I like my Gen 1, but the Gen 2 is better almost all-around. (Darn homelink omission!)
I think Tesla's Supercharger network's advantages over the SAE CCS DCFC network are VASTLY underappreciated:
- all SC locations are strategically located (both in terms of geographic location and also proximity to restaurants and/or shopping)
- all SC locations have a minimum of 4 plugs (and typically more)
- all SC locations have consistent power ratings* (*absent malfunction, at least. I know this is an issue Tesla needs to fix.)
- all SC locations are operated by one company (no worrying about subscriptions to various networks)
- low-or-no cost pricing (no worrying about paying absurd $/kWh or $/minute prices that are way more than gasoline equivalents)
Going on Plugshare and filtering by SAE CCS chargers, you will see a lot of pins on a map. But that's SO not the whole story.
That SAE CCS map is full of high-cost, subscription-requiring chargers, many with only 24kW of power and none with more than 50kW, and many times with only a single charger at a location, which is often a hotel or car dealership.
The "laissez faire" approach being taken to the build-out of the SAE CCS DCFC network in the USA -- combined its limited charge rates (to-date, at least) -- looks like a near-disaster to me (from a prospective BEV owner's point of view) and a hugely inefficient use of resources.