I see AWD as possible, but far in the future if ever, but not true 4 WD. I think Ford and Quigley have a deal that Ford will not step on Quigley's business.
Another reason, I think, is the roof height. The medium and high roof vans will never be true 4 wheelers. They are just too big and tall and Ford would have to redesign to fit a larger all-terrain tire. I don't see that happening.