By now, you've likely heard the rumors that the next-generation of F-150 will likely feature some extensive aluminum construction. Even if it doesn't have a completly aluminum body like the rumors say, it'll definitely be a large scale redesign. So it makes sense that Ford's engineers are getting started on testing the new truck early.
Motor Trend points out that the front grill is a few inches ahead of it's normal space, and there seems to be tape covering up wires in the bed. This means it's one of two things: A half finished SEMA reject, or a lightly disguised test mule. The fully camouflaged prototype that was also present leads us to believe it's the later.
There's a whole lot of rumor swirling around the future of the F-150. We already talked about about the likelyhood of them building it with an aluminum body, but Ford's also partnering up with Toyota for a hybrid. Indeed, this truck might be the test bed for that tech. It would explain the slightly broken looking grill, and the wires lining the bed.