The problem I see with it is that the low-ballistic-coefficient bullets of 'pistol-caliber rifles', in case of a miss (especially a high-angle miss), slow down to baseball-speed in six hundred yards or so, then start falling rapidly. On the other hand, the high-ballistic-efficient bullets typical of bottleneck cartridges like the 7mm Rem Mag that everyone around here seems to think is the bare-minimum suitable for whitetail, stay supersonic and stable for at least half a mile or more.
I just see more accident potential, with no real 'necessary' gain in terms of practical hunting needs.
OTOH, I'm betting most of the folks who will be using the 338 RUM and 7mm Rem Mag, or even the 308 Win, and such things were already using them illegally anyhow; I've seen and heard plenty of them afield over the past decade or so.
Personally, I will rely on my 44 Mag, as usual, but may want to 'blood' my previously-illegal 444 Marlin someday; in the meantime, I have several already-legal ones to take afield that I've neglected:
- 45 Colt (Marlin 1894)
444 Marlin (Marlin 336)
500 S&W (Bighorn Armory)
50 Beowulf (AR)
357 Maximum (Contender Pistol)