Nothings forcing you to replace them, they'll still work on Tahoe.

Also 2020 is the last Intel models. Late 2025 is the Tahoe release, and then you get 3 years of updates, meaning a total of 8 years of software updates for that 2020 machine.

Thats all pretty standard levels of software support, and again, it won't suddenly stop working in 2028.