My small, isolated opinion....
The word is, the EGR will go on the trucks after the first of the year. However, I can't help but think they'd do all the changes when they switch over the tooling, etc. for the new model year (admittedly, I don't know how much goes into a modern changeover). IOW, I wouldn't be completely surprised if all the '04's get it (but I sure hope not

). Disclaimer; this is my own theory, and it goes against just about everything I've heard or read.
I haven't heard what else to look forward to in next year's models. Hopefully the new variable-geometry turbos will happen but, again, it seems like they'd do all these big engine changes at the same time. D/C may increase the overall power ratings, but a few hundred bucks will do the same (box).
I decided not to gamble. Incentives were still good when I ordered, and the prices just keep going up (Truck-of the-Year didn't help that either). Any major problems with the '03's (early injector failure) should be figured out in the next 7 years, and covered under warranty.