I was told by one of the VPs from Toyota (TMS) that they will never bring a Hilux or any small diesel car or truck to the US. It doesn't make sense for them. The market here is geared towards gas guzzling V8s (trucks) or small displacement gas sippers (cars). There is no market for a small diesel. Plus the regulations from the US government on diesel emissions and safety requirements just make it not feasible. ALSO diesel costs considerably more here whereas most other parts of the world it is cheaper than petrol. Again, that is due to the emissions requirements, which increases fuel productions costs, etc, etc, etc. Trust me, I want a Prado as much (or probably more) than the next guy but it ain't gonna happen.
The ONLY diesel that we MIGHT (and that's still a BIG MIGHT) see from Toyota is a 1 ton version of the Tundra, which they are currently testing in undisclosed locations...