It will likely come in two different models with different screen sizes: one with a 4.7-inch screen and one with a 5.5-inch screen. This is reportedly the smaller version.
One possibility is that the larger iPhone 7 — the "plus" or "pro" model — could have a camera with two lenses.
Source.
The regular 4.7-inch version is expected to have a better camera too. Purported leaked pictures show an enlarged lens.
Apple might add a new color option, though. Some rumors peg it as dark blue, but a "space black" option is far more likely.
The biggest change will probably be — make sure you're sitting down — that the iPhone 7 won't have a headphone jack. Apple's probably going to use the space for a second speaker.
If you want to listen to music, you'll have to use Bluetooth headphones. Apple sells some nice wireless Beats.
Or headphones may be able to plug in through Apple's Lightning port, which is usually used for charging. It's unclear if Apple will include a set of Lightning earbuds with the iPhone 7 or an adapter.
Another advantage of connecting earbuds through the Lightning port is that it could open up new approaches to noise-cancelling earphones.
The home button is also likely to be redesigned. The new button will use a motor to simulate a click, as opposed to the current button which physically clicks. It'll probably use the same technology as 3D Touch.
This is kind of a no-brainer, but it's going to have a faster chip inside. Apple will probably call the chip the A10. Apple's chips are one of the company's biggest strengths.
More discussion of Apple's chip prowess here.
