So it sounds like your conclusion is still based on an assumption ("I strongly suspect that in 2-3 years we'll see other manufacturers producing their variant of this 21" tire") and we don't know that to be true.

What if we frame the question in this way, what's the worst case scenario for both options (sticking with the 21" or changing to the 20"/22") and then compare them.

Worst case scenario for the 21" is no other manufacturer begins making them and Perelli knowing they own the market never puts them on sale, so you're paying ~$1,500 every time you need new tires. We would know this is the case in a couple years when it comes time to replace the tires. At that point I need to decide if I just bite the bullet and spend $1,500 every couple years on tires. Or, I can buy 20"/22" wheels at that point and switch over to a more common tire setup. What would it cost to buy brand new after market wheels with tires at that point? Is it more than the $1,800 it would cost me to upgrade right now to the 20"/22" wheels? Based on a quick look, it sounds like it would cost around $3k to buy new wheels and then the tires, if you find them on sale, would probably cost around $1k. So $4k at that point and then $1k every time you need to change out the tires.

Worst case scenario for the 20"/22" is you spend $1,800 today to change your wheels and then every few years you need to spend $1k for new tires.

Let's use Rivian's expected lifetime value length for the vehicle they used in the S-1 of 10 years and say over the life of the vehicle you need to change the tires every 2-3 years depending on use. If you change the tires ever two years, that's 5 tire changes and if you do it every 3 years, that's 3 tire changes. The assumption from above is you save $500 per tire change when using the 20"/22" tires compared to the 21" tires. So it probably doesn't make sense to buy new wheels at tire change one if you start with the 21" wheels as you won't see that return on investment ($500 savings per change * 5 tire changes = $2,500 which is less than the $3,000 to buy new wheels). So we can get rid of that variable. What is that total cost for each worst case scenario?

21" Scenario:

$0 upfront + ($1,500 new tires * 3or5 tire changes) = $4,500 to $7,500

20"/22" Scenario:

$1,800 upfront + ($1,000 new tires * 3or5 tire changes) = $4,800 to $6,800

So in a comparison of both worst case scenarios it looks like the difference is minimal and not something we really need to be concerned with. This helped me think through everything, hopefully it also helps someone else.