Based on a press-release of Samsung it's likely that the Samsung Galaxy S6 will contain 4 GB RAM memory. Currently 2 or 3 GB in high-end smartphones and tablets is common.
In the press-release Samsung announces it has started mass production of its first RAM module for mobile devices with a capacity of 4GB. That would mean the smartphone will contain as much RAM memory as many laptops, e.g. like the Surface Pro 3 from Microsoft. It's for the time a company succeeds in fitting 4 GB RAM in a module for smartphones.
Given the fact that mass production has already started it's likely that the Galaxy S6, expected in the second quarter of 2015, will be equipped with the new memory module.
The advantage of the 4GB of RAM is that in quick succession 20 megapixel pictures can be shot and that Ultra HD video can be recorded and looked back without issues. The relative large amount of RAM also will increase overall performance.
Samsung reports the RAM improves performance with 50 percent over the current 2GB module and consumes 40% less energy.
Recently more information of the Samsung Galaxy S6 leaked, it's expected the body of will be made from metal instead of plastic. The phone should get a screen with a resolution of 2560x1440 pixels, a 20 Megapixel camera and a Qualcomm SnapDragon 810 SoC.
