The 4 cylinder turbo gasoline engines will offer decent low-end torque, not the same as a diesel, but decent nonetheless. The mpg advantage over a v6 gasser is there...if you don't haul or tow. The second you put a turbo gasser under load, it loses most of its efficiency advantage. This is why I think turbo gasoline engines really aren't the long-term answer for working trucks...and this is why we have yet to see a turbo gasser offered in any of the domestic 3/4 and 1 tons.
And FWIW, I think the modern diesel offerings (2.8l and 3.0l duramax, 3.0l powerstroke, 3.0l ecodiesel) have come a long way in terms of emissions reliability. There is even a rumor that Toyota may come out with a diesel design which reduces, or all together removes, the need for DEF and DPF.
Toyota Patent
Diesels still power the logistical backbone of the global economy, and likely will for quite some time. OEM's are still very much looking to improve those designs.