It's going to hammer resale value.
First - fewer new phones will be sold, that alone will affect resale.
If fewer new iPhones are being sold it means that more aftermarket iPhones are being sold, thus driving up aftermarket prices.
Anyone buying an iPhone in the aftermarket will be guaranteed a fresh battery, either by the seller or by Apple themselves, thus making aftermarket iPhone's more desirable and driving up aftermarket prices.
It's amazing how little people know about business.