According to my sale's rep (I just asked this morning) - it's the same shape but you're missing the part that goes to the back of the car.. the square "under" hole.
The frunk in Model X is much deeper than in Model S. The space lost to the front drive unit is more than made-up due to increased depth. Se my post linked below for pictures: http://www.teslamotorsclub.com/showthread.php/25703-What-s-going-to-be-at-the-2014-NAIAS-Tesla-exhibit?p=547782&viewfull=1#post547782