To add to what Kurtosis12 said, when Apple came out with the 16-series phones, they dropped the 15 Pro and 15 Pro Max at the same time. Only the regular 15 and 15 Plus remained, as price point models.
I would expect history to repeat itself, so by the time that you can trade in your iPhone 16 Pro, it is quite likely that you won't be able to buy new iPhone 16 Pro Max units from Apple any more. You might eventually see some start showing up in the Certified Refurbished section of the Apple Store, on a "catch of the day" basis.
Apple's price for Certified Refurbished iPhones is usually about 85% of the original list price.