We are dealing with text, no matter how complex the format; we are not dealing with video. Therefore, I find it very unlikely for you to need more than 4 GB of RAM for Trados Studio—unless there’s a memory leak, which is abnormal behaviour.
On second thought, their recommendation is for the total RAM of the system, which will be taxed by all running processes. So, some more RAM would not hurt, for sure. I think 8 GB have become standard nowadays, even on laptops.