I think the biggest issue is that the Hilux is in a segment of trucks that simply does not exist in the US.
Besides the diesel engine, the Hilux is a spartan, small, and basic 4wd utility truck. The Hilux along with the Chevy Dmax, the Terrano and the MItsubushi L200 are all small diesel utility trucks. They are marketed as such and designed for that market.
For starters the Hilux here in Chile does not even get offered with an automatic trans. In fact the only truck that does is the Mitubuishi L200 "Dakar" spec.
All the rest are roll up windows, manual trans utility trucks. Even A/C is an option.
When I mean basic, I mean they have a radio. That is it.
I know the thread is about the new diesel engine in the Hilux but I think we all have to look at the bigger picture. The Hilux is a straight up different truck than the Tacoma. It has a manual t-case, standard rear shackles (not inverted). An all metal pick up bed. A higher pay load. Bigger rear leaf pack. A very basic interior.
It's a different bread really. Just because they share the same front struts does not mean that Toyota is gonna slap a D4D in a Tacoma and call it good.
It's designed different, for a different purpose. I think the 3.0 and the new 2.8 D4D is designed the same way the whole truck is designed. Simple and reliable.
I know a lot of folks say that diesels are expensive to own and service. Which is true on a 1 ton Cummins or a Duramax. But the 3.0 D4D is about as simple and easy to service as a Corolla. It's very basic. Needs very few services. Basically oil and air filter's and the diesel fuel filter. You have the drivetrain gear oils like any other truck and a drive belt. The capacitys are much smaller than a big diesel so the price for gear oil and engine oil would be the same as a Tacoma.
It's cheap, easy and basic to own and drive for a long time.
But the key here is basic. It is a basic truck. Would a 3.0 or the new 2.8 D4D be a winner in the Tacoma chassis? I honestly doubt it. Not with the high way speeds of the US and the power demands of the current market truck people. It's just designed for a different need.
Maybe in Australia the Hilux gets a different trim package than here in South America. I know that in Argentina the Hilux does get an Auto trans but my point still stands. It's a different truck and engine for a different purpose over all.