Because it is four years old? Or because you're unhappy with your photos? You say you're not into "high end" photography, but exactly how noncritical are you?
The hard answer: figure out what it is about your photos you're unhappy with, do the research, buy a new camera that fits your needs. Portability may be a big factor, especially if you're into candids.
the easy answer: if you're thinking of a smart phone for other reasons and decide in favor of it, just go ahead and get the phone with the features you like. If you like the pictures it takes, do nothing, otherwise shop for a new camera. It's not as if you're investing in a Hasselblad. You may well be doing the equivalent by the time you've paid off your two-year contract for the phone service, but that's a whole other thing.
Personally, I don't see the phone replacing a serious point-and-shoot camera any time soon. Though, I saw in the Sky Mall catalog a telephoto lens for an iPhone, at a price you could barely buy a cloth to clean a Nikkor. I haven't personally evaluated the camera in the iPhone, or the lens, but have no doubt you get what you pay for.

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