Half ton truck market is so cutthroat that marketing plays a huge role. The diesel F150 isn't going to be a towing monster. I think they're gunning for "Best in class" fuel efficiency to make the marketing dept happy. Modern diesels cost a ton of money to develop, certify, manufacture, and own, so if they're doing it, they must see a demand for it.
That being said, I don't see a ton of EcoDiesel Rams around, and they've had some legal troubles in the last year or so regarding emissions compliance. IT's cost FCA some sales, and could cost them piles of cash too. Hopefully Ford doesn't regret giving their customers the option of an oil burner.