It's really hard for them to get away with any racing references in car commercials anymore. This is the C6 commercial that Chevy was forced to pull off the air:
Shows a kid driving, car jumping... all clearly a fantasy... no good.
I can't imagine them making 50,000 units and putting 6.1s or 6.4s in all of them. Especially since the SRT version of a vehicle usually comes out a year after the actual vehicle so the Skunkworks team has time to really tweak a high-performance package. And since the current SRT engine is a 6.1, I can't imagine they'd release a 6.4 that wasn't an SRT, nor do I think they'll have an SRT version the first year.
That rumor sounds awesome, but it doesn't make a lot of sense.