Well it's really not possible to tell without actual first-hand experience, and most of use won't have that until who knows when, but I wouldn't worry too much if I were you. I don't see why the learning curve for Fallen Earth should be any steeper than that of other MMOs out there.
How long do you guys think it will take an average player to familiarize himself with the game, get the basic feel of it, and get to a level where he can keep his head above the water and still have fun? I ask because right now FE seems (while fascinating and all) a little too complicated to get into for a casual player like myself.