I was assigned the delivery date and time at Fremont factory sells center on Dec 31 2019 at 8pm (as many people), I double confirmed with the employee at the Fremont delivery center and the factory sells center and both gave me the confirmation. But then a lady called me and told me that my car cannot be delivered before the end of 2019 and SA would contact me. So far no one ever tried to contact me.
You might still get a car since some people will get cold feet, etc. They are *really* disorganized at end of quarter with all their internal volunteers that don't know what they are doing! It is a zoo in my experience and very fluid situation.
I will be volunteering this year on 12/31 and volunteered last year to show people how to pair their phones, etc.
Here is my 9/30/2018 last day of 2018 Q3 Model 3 story: (briefly) I'm a stockholder so was doing them a favor I could have waited until Q4 with same tax credit.
1. They let me out of my $2K+/month March 2016 Model X P90D lease 6 months early so I could buy a Model 3 Performance. Note it had to be a Performance model to cover their hit on the early lease return. Okay - whatever.
2. They were supposed to home deliver it to my Fremont house on 9/30 midday from their home delivery hub south of factory on Kato (used to be old Fremont service). No show and no contact. WTF?
3. I drove to said home delivery hub. Manager searched "no cars" for home delivery we're really sorry. Why don't you go to the Fremont Delivery Center to see if they can help you?
4. Drove to Fremont Delivery Center and talked to a manager who searched inventory: "We have a VIN we can give you, it's not Performance, and it is black instead of white interior, would that work?" [me: Yes! I didn't really want Performance anyway since my wife didn't like it whenever I "launched" our Model X].
5. I asked like 5 times "Are you sure I can return the X 6 months early to buy this Model 3 Dual Motor w/ AP"? They called "Ownership Loyalty" and got approval.
6. Closed the deal on the iPad around 11 pm. Hung around to help other people with basic operation of their new cars.
7. Left our Model X parked where they told me to.
8. It took until January 2019(!!!) for TSLA and US Bank to inspect the 2016 Model X P90D and close out my lease. Good thing I saved a bunch of photos to document the condition. There were no extra charges except for some extra miles.
Bottom line: Tesla is all hands on deck 12/31/2019. If I were in your shoes, I would just show up with my original email invitation (play dumb) and try to pick up your car. if they can locate a Model 3 that meets your requirements they will definitely sell it to you to help their 2019 Q4 and 2019 annual sales and financials.
You might even see Elon there if he's in town at this "event". He dropped by on 12/31/2017 with former CFO Uhuja at Fremont Delivery Center. My friend said CFO was personally "approving" personal checks to pay cash! No kidding.
Worst case you can enjoy a special Tesla event with DJ, food and drinks (if it's like other "events" I've attended), and meet some other owners.
Good luck!!
Russ