All the information to-date indicates that the Galaxy S IV may not look too different from the Samsung Galaxy S III, but since the video shows a dual-SIM variant set for China Unicom, there is a chance that the single SIM version could be thinner.
Additionally the demonstrated version features a 2600 mAh battery. If this battery (or better) makes it to the final version of the Galaxy S IV the device will surely last a full day.
The demonstration also shows that the device is running Android 4.2.1 Jelly Beam with a new version of TouchWiz. The handset is expected to receive the Android 4.2.2 update around a month after it launches.
source – 52 Samsung