There are a lot of good theories and I think everybody's right on some sense. Market saturation, upgrade cycles, the holiday quarter drop, this all contributes to the downshift in sales.*
My small theory? Phones are just getting too damn good. I used to upgrade my android phone every few months hoping the extra speed would take care of the lag. Or there were camera upgrades or software enhancements or new better screens.*
Now? Our wish list of must have features are dwindling and we're more happy with our phones now than ever. After being a new phone every few months kinda guy and getting an iPhone, I feel like I could finally have a phone for more than a year.*
What's to upgrade for? The processor on my 4s is fast enough, screen is just about perfect in my eyes, camera replaces my point and shoot and 4g is something I had on my last phone. I just don't care about it right now. I get a solid 3megs in my area with my 4s and what would I be doing to need more than that? I can load YouTube videos with a 2 second buffer time. Web pages load quick. Siri comes up quick. What else do I need?
I'm sure a lot of *people feel content with their 4's too. And with a lot of us having new iPads, we wouldn't care about upgrading to the next iPhone for a bigger screen.*A lot of what we want at this point is software and that'll make a lot of us look forward to ios6 more than the next iPhone