It'll Have a Flexible, 5" Display
If rumors are to be believed, the Galaxy S4 will be the first Samsung device to utilize a flexible OLED display. That doesn't mean the phone itself will be flexible, but it could be that the display slightly curves. OLED displays are also supposed to be thinner, which could mean the next Galaxy flagship will be ultra slim in the hand.
The Processor Will be Really, Really Fast
On September 19th, Android Authority spotted a mysterious device in a test posted to "Power Board." The device – called the TE4 – featured a Cortex A15 processor, clocking in at 1.7 GHz, along with a Mali-T604 GPU. Sure this might not be the Galaxy S4, but what other phone would Samsung pack with such advanced technology? If it is so, it'll be signficantly faster than the current model.
It'll Have a 13MP Camera
Another mysterious Samsung device showed up online that appears to have a 13MP camera, capable of taking images with 4208 x 3120 pixel resolution. We don't know for sure if this is the Galaxy S4, but it seems likely.
It'll be Coming in March
Of this we can be almost certain, as Samsung tends to release their Galaxy flagship devices after Mobile World Congress. The date has been backed up by a report by Korea Times.