According to a user of the Korean website naver.com, Samsung is currently working on a Galaxy S4 model with LTE-Advanced connectivity, while this model probably won’t be released in the United States or Europe, it does seem that the company is going to add a more powerful processor to the device. The Galaxy S4 LTE-Advanced (SHV-E330) could possibly feature the 2.3GHz quad-core Snapdragon 800 from Qualcomm backed by an Adreno 330-gpu and 2GB of RAM. It will of course also support LTE-Advanced for faster data-transfers (only available for a few regions).
Possible specifications of the Galaxy S4 LTE-Advanced (SHV-E330).
This device should be launched in August or September, we might learn about this version during the Samsung event on the 20th of July.