VGC numbers are notoriously unreliable when it comes to pre-orders. I wouldn't read that much into it.
There's no real signs or rumblings of the game struggling to pick up traction so I think it'll do just fine. More interesting will be the split between XOne and 360 sales for me what because of the Fallout 4 thing. Will probably be a knee-jerk reaction which one gets booted to a Christmas present.