Expected iPhone 5s cost after iPhone 7 release?

What do some of you guys think the expected cost of a new and a used iPhone 5s will be after the iPhone 7 comes out?

Probably 50$ at the lowest or Maybe itll be like the 5c and be free on contract but i doubt

After each release of the iPhone, every other model decreases in price by $100 from retail (retail for the lowest gb model is $850)
So by the iPhone 7, the iPhone 5s it will retail at 450-500 or free on contract but that'll usually mean that Apple itself will only sell 8gb models by then