Wired wrote a pretty good article talking about what to expect from the 3G iPhone and I have some things to say about it.
Radio
It is all but officially confirmed that the Infineon chipset will be used on the 3G iPhone, if you find mention of it in source code on the phone it is pretty much a dead lock that we will see it.
Camera
I don’t know for sure if we will see a 5 megapixel camera in the 3G iPhone, I wouldn’t be surprised if we did but I don’t understand why they would really need to give customers any better of a camera, no matter what anyone says the 2 megapixel camera in the iPhone is a pretty good camera. Now when it comes to more options while taking pictures I’m pretty sure we will see that, if not I’m sure someone will make a replacement image capture application for the iPhone with the SDK.
Hardware
I don’t think that there will be any hardware changes when it comes to the overall look of the device. I’m pretty sure Apple doesn’t want to make those early adopters angry again, I don’t think that we’ll see any changes to the look of the device until next year (when the original iPhone owners 2 year contract runs out).
Software
We’ve already seen pretty much everything there is to see in the new iPhone software, but what we haven’t seen are all of the 3rd party applications that developers are furiously coding right now that will launch at the same time as firmware 2.0 or shortly after. I’m really excited about this part and think it is the most important thing to happen to smart phones since the smart phone was invented, never before has a single company released a phone and then released the ability to code 3rd party apps that has gotten everyone as crazy about it as the iPhone.