[stephenr]

Apples 'cheap' iPhone is last years (or the year before). And it works, because unlike most Android devices that get very few updates, with long delays (or no updates, ever, for the very cheap devices), they support devices with newer OS releases. A 5S will still run the latest iOS.

[kylnew]

I agree that appears to be the way they are going. If they are working to extend the life of devices even further in coming years that seems to support this direction.

[stephenr]

Over time the resources required to run the OS itself should go up slower than the hardware has increased in capability in the last few years.

While the next iOS release may require an iPhone 6 or 6S, I expect it will be quite a while before it changes base requirements again after that.

[kylnew]

The only thing that the iPhone 6 can't do which I know of is ARKit, which seems to be one of the most hardware intensive things phones are capable.