Ashful
Minister of Fire
Yawn.
Fuel mileage would have to be spectacular (30+) to make it worth swallowing the likely hefty price premium as those numbers are sub-standard for many of the new half-tons with gas engines. GM's 2014 5.3L V8 is making 385lb ft of torque as well as an additional 145HP over that baby Cummins, and it will be in the vast majority of new Sierrias/Silverados. With the cylinder deactivation and direct injection (new for 2014) it should get north of 20MPG on the street. Seeing is believing of course.
I think a big part of the marketing problem is that diesel has always leveraged high reliability and lower mileage against a much higher initial cost. However, for the most part, those buying NEW 1/2 ton pickups are not the folks putting the high mileage on them. How often do you see a first-owner 1/2 ton with 200k miles on it? More often, it's the second (or third) owner seeing the odometer hit that mark.
Put otherwise, if I'm going to trade my new truck in at 70k miles, why the hell would I dish out an extra $8k for a diesel? It would appear Ford knows this.