As one of my friends pointed out, the only 'downside' of this box is that it doesn't really match with the other boxes on the art department. For the other 3 boces, they've used original art, but for this one they've gone with movie stills. While it doesn't really bother me, I do have to agree with him that this box feels somewhat like the odd man out because of it. Wouldn't have mind to see some nice TFA art that hasn't been used yet. (This was actually one of my pet peeves with the Special Modifications book, in that they used art from the Essential Species Guide instead of creating their own.)
But from a marketing standpoint, I completely understand why they did it. Just looking at the box from afar, you can immediately tell it's The Force Awakens. Seems like THE perfect product to get new people into the game, especially younger people who just got introduced to Star Wars through TFA.
Could also be that it's placeholder art.
A number of companies do that, especially if a product is still in development.
Given it's been a long drought since FFG made a product announcement, they probably wanted to have something on hand for May the Fourth, and so opted to show a box with the movie-inspired cover just so that they'd have something to show.