Perhaps this is because Apple is reportedly going to make the screen bigger, offering a 4.7-inch version of the phone. The current phone is 4-inches.
Apple is also reportedly going to do a 5.5-inch version of the iPhone, but that seems less likely right now.
This is the last major physical change Apple can make to the iPhone. Android phone companies have been producing phones that are 4.7-inches and bigger for years. iPhone owners have been lusting after a big screen, and are now they are going to get one.
With all the hype for the iPhone 6, illustrators are making renders of what they think it will look like based on leaked schematics, and rumors about the screen size.
Designer Martin Hajek (follow him on Twitter at @deplaatjesmaker) decided to do his own renders of what the iPhone 6 will look like. They're probably the best attempt at it we've seen so far.