I'm not sure anyone knows for sure, but what I can tell you is that when the hellcat platform came out in Q3 2014 they had similar production problems with not being able to get 3rd party parts and far more people ordered than they anticipated and they only ended up making about 7,000 total hellcats from august of 2014 when they started production to august of 2015 when they stopped production and switched to the 2016 models and about 900 people (me included) got their order that they placed and had a VIN assigned canceled.
The similarities between the launch of the Hellcat and the Launch of the TRX is it is a similar engine and its coming from the same company and both are only built in 1 plant. The TRX is launching during COVID so I would Imagine production "hiccups" are worse in 2020-2021 than they were in 2014-2015 and production did start on the TRX until the middle of December which is 4 months after it started in in 2014.....Assuming FCA quits making 2021s in Q3 of 2021 like they have on all of their other platforms and that they are capable of making similar numbers of TRXs as the first year of the hellcat if you take out 4 months of production you are looking at only around 5000 TRXs are likely to be made in 2021 model year. And from what we can tell at least 3,000 already have VINs (unless they are skipping numbers)
All this to say it is entirely speculation based on past performance and anyone in the market has heard "past performance doesn't guarantee future performance" but so far FCA hasn't given us a reason to believe they are doing better with this launch than the original hellcat and if it were me and I had an order without a VIN I wouldn't hold my breath that the order would actually get filled with a 2021 but if they cancel your order and you hold onto it they will likely offer you a 2022 model for the same price as the 2021 which is what they did for me on a 2016 hellcat and they will definitely prioritize your build first. But if you can find an order with a VIN that has the options you want I can't see them not being able to build at least 3,000 trucks
As far as having $100k in liquid capital set aside for the truck, it doesn't do you much good to do anything but park it in the highest yield savings account you can find if you are going to buy one regardless of the model year. (I think my savings account with my TRX money is at about 1.2%) This advice is assuming even if the market with the fed printing money for the second COVID stimulus package, the changing of the guard, the increased lockdowns, and cooperate and personal tax hike doesn't tank and manages to grow if you get your truck in the next 12 months whether its a 2021 or 2022 if you don't hold a stock or mutual fund for 12 months or more you end up paying 40% short term gains tax on the gain so its not worth the risk IMO and if the market corrects for all of the above reasons its not worth the risk of your $100k in cash being worth $50k when you need to take it out.
But opinions are like assholes, Everyone has one and they all stink so unless you are my kid you don't have to listen to mine if you even made it this far in that novel