At least in the US, most customers upgrade their phones on a 2 year cycle. The iPhone 5c is an upgrade over my iPhone 4s and the 5s appears to be a significant

At least in the US, most customers upgrade their phones on a 2 year cycle. The iPhone 5c is an upgrade over my iPhone 4s and the 5s appears to be a significant upgrade. Each generation may not be a huge improvement from the previous one, but it's always a pretty big improvement over 2 generations ago. I would be amazed if folks were upgrading from the iPhone 5 to the 5c in significant numbers.