IMO a HD 3.0 turbo gas motor that matches the 6.4 will be too highly stressed to make the mean engine life of 300k that we keep hearing for HD trucks.(think peak cylinder pressure) IF it's paired with a hybrid system then it could be a different story because the max output of the engine could be reduced and peak torque won't necessarily be needed as often with the electric motor there to boost torque on demand. There's still the issue of fleet users have to be buying them, they are the majority of HD truck purchases after all...think economies of scale.
I do see Ford being the first to bring a turbo/hybrid system to the HD market, and it is something that I would consider given my personal usage conditions...though it probably would turn my stomach to do so! The Ford part that is, I had a turbocharged DD at one point and it was great and had power everywhere in the rev range without having to scream to get up to speed quickly.
I also believe that there's a lot of regulations left to sort out here for trailering. I would imagine that in a hybrid powertrain the ICE (internal combustion engine) would still NEED to be able to maintain the standards(minimum speeds etc.) without the electric motor helping out. This is the same way that EV's still have relatively large brake rotors and calipers as you still have to be able to stop the vehicle in a reasonable distance even if the regen feature has failed.
I think the problem is that a system like this increases the cost and the gains are not worth it...so a gas hybrid might be 2,500 more and a diesel hybrid might be 3,750 more(50% increase). But in the end your mpg only goes up by say 5mpg(20% increase), it takes a long time to recoup that extra "investment." Of course this mpg increase pretty much only applies to trucks not pulling trailers, which can be rare in the HD world. (Keep in mind these are just WAG's and guesstimating based on 20mpg for the gas hybrid)
Lets be real, with the majority of vehicle purchases people aren't looking to have a break even point at 150k...they're likely going to sell/trade either before the warranty runs out, or before 100k. Don't get me wrong, there's definitely people out there that drive their vehicles into the ground, but it's just not the majority in this day and age.