Naming the new iPhone
The next iPhone will likely be called one of three options: iPhone 5, iPhone 6, or the new iPhone.
iPhone 5 will never happen because it lends itself to obvious headlines such as "Apple finally releases the iPhone 5" and "iPhone 5 arrives a year late". Neither of which is flattering.
iPhone 6 won't happen either because normal consumers know the iPhone by its external appearance. Under that context there are three iPhones: the original iPhone, iPhone 3G, and iPhone 4. Apple can't and won't create confusion by skipping over 5 to 6.
The new iPhone will be called "the new iPhone", joining "the new iPad" and the rest of the Apple lineup (MacBook, iMac, Apple TV, etc) with no numbers. After this year, they won't even refer to new hardware as "the new iPhone" in print, it'll just be "iPhone".