I don't think the market is really there for a diesel half-ton. They're the same size as a HD, cost almost as much, and even a diesel option won't give that much of a FE benefit now that everyone has to have 400+HP and as much torque as a big rig used to have. I do, however, think there is a market for a compact diesel PU. It's a market segment that doesn't exist and it wouldn't steal sales from the HD segment.

Keep in mind also that much of the diesel premium is returned at resale, unless you happen to have bought one of Ford's recent dogs. Today, with the draconian and complicated emission controls, there is no purpose in owning a diesel HD unless you really need it. A half-ton V8 with cylinder deactivation will deliver the same highway FE for thousands less and on a slightly cheaper fuel.