So does this mean they are optimising to get it to 60fps?
Or is there bullshit excuse about being "cinematic"?
More RAM won't really help for a better framerate. Keep in mind, the GPU is still limited to drawing a certain number of polygons per second and shader core clock.
What would be possible, with still so much RAM left, is the ability to load a lot of generic stuff beforehand. Like first person models, world models, enemies, textures, etc... Stuff that's used nearly all the time. Imagine pressing start on the title screen and continuing your last save. Two seconds black screen and bam, you're instantly already playing! And from that point on, more loading screens as you progress. All because the game cleverly loads future needed assets.
That is, if they actually implement that.
For all I care they can use the last 3GB to make the most spectacular Rico death scene ever.