I have spoken to the fine folks at TST and Bully Dog, and they both have "test-bed" trucks that they've been pouring fuel to and making programming adjustments to. TST told me, last week, that they've had their test-truck on the dyno and improved its horse-power peak by well over 100 hp, but they're still sorting out the DPF/emmissions issues.
Bully Dog had a June 1st release date for their 6. 7 electronic programmer, but that's been pushed back, because of "issues" with the EPA crap. Basically (Bully Dog tech support related... ) they're trying to balance the amount of fuel they can flow (plus timing advances) with the vehicle's needs to perform "regens," and how to avoid clogging the DPF too quickly. The tech guy at Bully Dog said that they were considering offering an "off-road" version of the exhaust system that wouldn't be EPA compliant in order to get around all the problems they're encountering with clogged particulate filters.
I don't think these new trucks will ever be "tweakable" to the extent that the 2nd gen/3rd gens were -- at least not in the immediate future. Cummins/Dodge spent years engineering an EPA-compliant version of the motor and electronics, and it's going to take more than six months to undo that gordian knot without risking damage to electronics, drive trains, warranties, and what not.