From Cummins, they will not produce the 5.9 for ANY application in the US in favor of the 6.7. Overseas might still see the 5.9 but I doubt it.

Diesels in Europe mainly sell because they are a lot more fuel efficient compared to gassers. And we have a lot of small diesel engines which help economy, you´ll mainly see 1.8-2.2 liter diesel engines here. The biggest engine so far is the 5.0 V10 from VW which only goes into the Phaeton and the Touareg. Gas and Diesel price here is more than double the price you have to pay in the US. Diesel is usually about 20 cent lower in price per liter, but taxes for a diesel engine is a lot higher, about triple the price of a gasser with the same displacement. That´s why diesel mainly works for people who drive a lot of km´s. I think we´re also quite hard on emissions and smog regulations. That´s why more and more new diesel cars have a particle filter. From what I´ve read the new 6.7 Cummins will get such a filter either. But performance and low emissions can be done with the right engineering. BMW soon releases a 3.0 I6 diesel with 286 hp, that´s 95 hp/liter.

Bombing the new 6.7 with a particle filter will be a hard work, the more soot the engine produces the earlier the filter system has to burn this soot. Upto the point the ceramic filter just melts because of the very high temperatures (above 1000° C, don´t know what that is in °F), replacement will be expensive I bet.

Where theres a will theres a way, you know they will have ways to elimante sensors, cats etc. Chips and programers will become more advanced and have even more features as these powerful engines become more computer controlled. I for one am exited to see what EDGE and Smarty companies come up with.