The iOS 7, M7 and A7 Combo
Don't you think the improvements in iPhone 5S would keep it way ahead of the previous iPhones? I mean it's like Apple has set a boundary between the iPhone 5S and the previous iPhones (and the 5C) because of these 3 improvements and maybe a little bit more with the fingerprint sensor.
What I'm trying to say is this. When developers develop around the iPhone 5S, they would be dealing with three new changes, major changes. First and foremost, the new UI of iOS 7. They would fit the UI and all the physics in their apps. Next is the M7 chip. Of course, developers would utilize the M7 for some processes to get some load off the CPU. Last is the A7. Developers would develop around the 64-bit architecture of the chip and its new ARMv8 instruction set. All in all, this would make the previous devices significantly sluggish and may cause some incompatibilities because the developers are now developing for a more advanced device. Combine iOS 7's new UI and physics with the ability to offload the CPU by utilizing the M7, the new 64-bit architecture and the new instruction set of the A7. This would make the apps developed around the 5S significantly more demanding than the previous ones and in turn, would cause the previous iPhones, even those equipped with the last-gen A6 processor, to struggle with the new apps. Of course, I know that some developers know how to handle their apps and they consider the older iOS devices but I'm just saying that this could be a turning point for the apps and iOS as a whole.
Please correct me if I'm mistaken about something in developing apps, I'm still a frosh and I haven't started programming yet so I don't really know everything about programming, maybe even anything about programming. And, sorry. I'm not good at putting my thoughts into words.