I am on a 2 year contract myself. I might keep it for an extra year to make it 3 year but doing iOS development I am in the few people who have a legitimate reason unlike most people who think "it do for an extra year." Also battery depuration bothers me which if I am going to have to spend £60 on a new battery and lose my phone for a few weeks as I am quite outgoing. And condition of the phone. Battery packs may be a solution for me?That describes how I feel about my 6s and the iPhone in general right now. I like it a lot and it serves me well. But incremental updates as of late aren't as exciting as they once were and, at this point, I'm questioning whether or not I will upgrade to the 2017 iPhone when my 2 years are up with the 6s. Maybe I will, maybe I won't; it all depends on the condition of the 6s and whether or not the 2017 iPhone will debut some amazing, must have, feature or not.
But think about this. If apple has sold 1 billion iPhones and they only take up 20% of the market it works out that there is 5 billion smart phones are out there or 5/7 people have phone.
Also look at this: http://www.pewglobal.org/2016/02/22...age-continues-to-climb-in-emerging-economies/
Most people will have phones already in developed countries and the main gap is in Africa which is missing the infrastructure and usually cannot afford an £300 smart phone - £99 is a stretch for them