KGI analyst Ming-Chi Kuo says the new phone will be available in black but also gold, and will match the current iPhone's the screen size, sticking with a 4-inch screen.
He also predicts the phone will tout a fingerprint scanner, as part of a sapphire home button.
The analyst also predicted Apple will boost its processor to a new A7 system-on-chip design with 1GB of LPDDR3 RAM, expected to be of Apple's own design based on the ARMv8 architecture.
AppleInsider reported that since Apple controls both the operating system and hardware for the iPhone 5S, it can optimize the faster LPDDR3 RAM spec for the A7 SoC, keeping the amount of addressable memory to 1GB.
Kuo also said he expects Apple to add on a new option for 128GB of on-board flash memory, which Apple added to its fourth generation iPad in February.
Finally, Kuo said he doesn't see Apple implementing near-field communication (NFC) in the iPhone 5S.
The next iPhone(s) is expected to be announced at an event on 10 September.