well iphone 15 is already cheaper than 14 was at launch so.

iPhones are so mature by now, I do not expect huge inovations - so you can use them basically until software updates stop. So every year you do not buy now, reduces the useful lifespan that you can get out of it - not sure that the price reductions, which will come until iPhone 16 comes out, compensate for the reduced useful lifetime.

September 2024 when the iphone 16 is launched.

I saw 15 basic models selling for €100 under msrp during black friday on one retailer in Finland.