When I think of a new iPhone, you know what gets me excited? More storage, bigger battery, MORE RAM (seriously I work in game development and the RAM on the iPhone was constantly an issue when doing mobile projects)! Hell even a better camera is nice.
Not once have I ever thought "Self, you know what would make this phone amazing? If the glass curved around the edge. What would we do with it? Not sure, but look at those curves!!!". I can't recall ever having a conversation with anyone aside from my wife regarding the look and feel of the phone (and that was really a conversation about how little I liked the new form factor compared to her old 5s).
Want to make the next iPhone a must have for me? Give me a phone that improves the internal specs, is shatter-proof (ah but then what would apple do about all that lost $$$), and is water-proof (yes I can buy a case...but wouldn't it be nice to not have to carry a box in my pocket?).
My interest is fading fast, and all these rumors tell me is the next iPhone is going to be total garbage BUT WAIT for the one after, it might have some gimmicks.