Not necessarily gpus but also like every computer part
When manufacturing capacity exceeds demand and manufacturers need to clear shelves for new models.
Considering that demand is currently expanding faster than new wafer fabs and support components can be built, that is unlikely to happen in the foreseeable future if ever. If TSMC's 3nm and Intel's 7nm-and-beyond perform well, maybe bargain hunters will be able to get new-in-box old-gen parts at a discount in 2-3 years to keep all of that still-good-enough-for-most-people 5-10nm equipment printing good money.