The last iPhone upgrade we will get will be a better battery
Rumours abound, as they do every year, concerning the upcoming iPhone 15(s) and the majority of the changes are relatively minor. Some software improvements, a USB-C port, an Action Button and the usual improvements will likely arrive, but the one thing 99% of people need is a battery that will last a decade of charging.
For me, and the vast majority of everyone else who do not need to spend money on small changes, it is only the battery that stops them from keeping their iPhone for longer. You can of course pay to have your battery swapped out, but it seems that this process triggers some people to then upgrade. They want new, they want the sleek unboxing experience and it does not take much to push them to shell out a lot of money for 95% the same experience as they had before.
The key for Apple, a company that makes a phone that will otherwise work acceptably for a decade, is the limited life of the battery inside. If battery performance jumps in one big leap Apple, and many other phone makers, will be hit hard.