You are form the west coast so in the event that Austin is for Eastern US, you will not get an Austin vehicle. If you do some reading on here (specifically this thread) you will see that Austin has only certified the MY AWD (not SR or LR or P). There are many reasons for this and why they may not need to certify other models. The only thing stated about Austin was that they project to do some customer deliveries Q1. No one knows which model or where they will go. Also, based on the newly certified Austin AWD MY, the batteries do not seem to match the hype that has been built up around battery day.
In your situation, there is only one known fact. You have a Fremont VIN and Fremont is the only place shipping vehicles right now. If yhou want a car at all, you should take what you have. Since you have a VIN assigned, you need to read your order agreement and see if you can even place your order on hold at this time. If you reject this VIN, you may have to take the next one assigned to you whenever that is. If one had to place a percentage on your chances of getting a MYP with 4680 cells from Austin, I would put it at less than 5%. Your odds are higher of getting a 4680 from Fremont when they switch over (which they will at some point, just don't know when they will have the 4680 production capacity for this. Or if 4680s will ever match the hype. With the scarcity of nickel, Tesla might be shifting new battery production (read all 4680) to a different chemistry, possibly LFP which is for "SR" cars. If you want LR or P you might have to stick with 2170. Keep in mind, the best performing car Tesla makes, the Model S Plaid uses 18650 cells so don't read too much into the 4680 hype that it will lead to faster cars. It CAN lead to this if that was Tesla's goal but their goal is to save money and maximize profits so they will focus on saving money on production and worry about performance later.
Long story short, if you want a MYP (you did order one), then you should take this one.
You don't get to switch to another model at the price it was when you placed your order. The pricing for your order is locked in. If you ordered a MY, then you change wheels and colors and keep the same base model price. Up to this point, if you changed anything, your base model price shifted to the current price (much more expensive). This will allow Tesla to push rejected cars of different colors to those who have been waiting th elongest if they are willing to change colors (most common).