Thing is, I never expected the 4S to be anything more than it was, Apple don't make massive leaps year on year. Hardly any companies do, and I include Android handset makers in that, it's simply not in their interests.
I reckon Apples problem all surrounds their protracted release schedule of the 4S and eventually the 5. With the exception of nerds like us who frequent forums and read tech blogs, the masses are happy with a phone for a couple of years. As such, I don't think the (imo) purely spec bump & Siri of the 4S was the problem. It's that it came out 6 months too late, and the weight of expectation meant it was always gonna be a disappointment. Now you've got loads of people, myself amongst them, with an out of contract two year old phone that, specs wise, has been blown out of the water by android phones. These people are itching for new hardware, and the next iPhone is still months away.
I'm from the UK and contract free these days, I bought an International Note last November, largely due to gadget lust. I still personally prefer iOS to be completely honest, but the screen of the Note renders my old iPhone almost a curiosity these days. All silly speculation at this stage I know, but the highly dubious leaks surrounding the next iPhone leave me completely cold - taller 4" screen with sub 720p resolution, yaaaaawn. I know the Note is fairly niche, but I wouldn't even consider anything under 4.3" now, and I expect a lot feel the same.
My extremely long winded and boring point is, I consider myself a BIG Apple fan (not fanboy, I like tech generally and have a whole host of non-Apple paraphenalia), and if I've left their phone in the dust and not entranced by the rumoured next one, ouch, there's quite likely a load more that feel the same.