We'll see about the EPA soon... Between Trump and consumer demand for big vehicles, they're going to have to back off, or better yet, go away, for now. The manufacturers aren't able to build full size vehicles at a reasonable price and meet MPG mandates yet.
And the main source mentioned, Allpar, isn't the most accurate in my reading and experience. They've been suggesting new engines, models, and vehicles for years with hardly any of it being correct. If anything, the Hemi will be phased out over time. There's simply too many products, from Chargers to Grand Cherokees to Ram HD, using it (5.7 or 6.4). And speaking of Ram HD, 'real' trucks' aren't ready for twin turbo V6s. Too much weight for a TT to ever get off boost. They might lose the 5.7 there as the 6.4 supposedly gets the same mileage, although it technically doesn't matter in that class.
Regardless, I think we have 15, maybe 20 years before pretty much everything new is electric and self driven anyway. I just hope that that antique vehicles are still given exceptions and aren't mandated in to the junk yard.
As for making a turbo option, what's the point? The 5.7 Hemi is just as efficient or more with fuel as the Ecoboost (unless you start talking 4 banger TT, and that won't do in a pickup. Maybe the cars), and is cheaper to make and sell. They're also less parts to worry about.