The iPhone 5S is expected to maintain the same size. Some rumors point to a design without a hardware home button allowing Apple to create a completely flat surface. Now a new rumor from China says that Apple has a big surprise in the iPhone 5S. The screen resolution of the 4-inch display is supposed to double. Today the iPhone 5's retina display has about 725,000 pixels. The new iPhone 5S is supposed to have 1.5 million according to WeiPhone.
This is not science fiction as for instance LG already announced a 5-inch display with 2 million pixels last year (full HD, 440ppi).
The iPhone 5S would also have a narrower bezel compared to the iPhone 5.
Apple is expected to unveil the iPhone 5S this fall.