Just speculating here across the board ... but simple logic and some (supposed) common sense SHOULD lead everyone to believe that as smart phones get more more expensive ... and as we all dip into some sort of agreement/plan/contract where upgrades are not really cost effective (relative term there) until after about 18 to 24 months ... that purchases of smartphones is going to dwindle, regardless of brand or carrier. Especially considering that (as stated above) the newer models with newer features really don't have a whole lot of "more" about them than phones that are only a year or two older.
Yes, they are faster ... better cameras ... more robust functionality ... etc. But "we" have to remember that most of the consumers out there don't think about their phones like we do ... or use them to the level we do. We may have what seems like a huge forum here, but "we" are still a very very small part of the consumer market for smartphones.
This is one reason a lot of people prefer the Apple phones ... take the phone out of the box, turn it on, answer a few questions, download a few apps, and go. Customization, or worrying about exactly what features are in the facebook app on an iphone vs the facebook features on an android phone NEVER crosses their minds ... Adding widgets, customizing the look, etc ... MOST people obviously couldn't care less. They just want/need a phone that they can call on, text on, and play with a few of their favorite apps.
To be honest, my GS4 would still be perfectly acceptable to use, at almost 3 years after it originally came out. Only things I'd really be missing are a better camera, and faster hardware. But the phone still works perfectly, and I could have saved a good amount of money by NOT buying a GS6. I only did because I like tech stuff.
I have a very large extended family ... some of them have gone to the iphone 6 ... but most of them are on iphone 5's, and one even has a blackberry phone he got a couple years ago, and refuses to upgrade simply because he can already do everything he needs to do on that phone.
Long story short, if any of the smartphone companies think that simply offering a new model each year or so that is only slightly upgraded w/ faster hardware and a slightly better camera is going to cause people to rush out and trade in their old phone for the new one ... they are mistaken.
Another aspect is ... for a while, the whole smartphone boom was driven by people moving from normal old phones to smartphones ... and then the initial learning curve by smartphone mfg's to quickly make newer versions of smartphones with MUCH more capability (think when Apple added a flash to the camera ... or a front facing camera) ... those type things do make a real difference in phone capability ... But just making the camera 'better' ... or making the phone a little faster/more responsive ... that just isn't a huge selling point to MOST people.
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