OTOH Leaf is a proof that old batteries can be replaced and upgrade an old car.

Original Leafs were sold with a 24kWh capacity. Current ones have 48kWh for the same price, and 64kWh replacement batteries are available. So you can go from half of the crappiest range to 3× more range than when the car was brand new.

Old batteries with reduced capacity don't even have to be thrown out. There are projects that reuse old Leaf batteries for grid energy storage (any capacity is useful when they're sitting on the ground).

I'm betting that the current-gen mainstream cars will benefit similarly, especially that production volume is orders of magnitude higher now (lots of brands share the same platform and battery modules).