I think it's actually worse than that.
Engine designs that needed a carburetor needed a carburetor.
Essentially, the only "magnum" cases that needed a belt were the original H&H's that had very little shoulder.
The useless belt on "magnum" cases was there because of marketing. Due to the wildcatting craze off the H&H's, Joe Average thought a magnum had to have a belt and the ammo makers were happy to oblige this fantasy. Of course there were some, like Charles Newton, that knew better.
We finally have magnums that make sense yet there are those of my generation (baby boom) who cry like little girls if anyone points out the idiocy of the belted cases we grew up with.
As a handloader, I'd always choose a 7 PRC over a 7RM. Of course, I'd sooner use a 6.5 CM or 270 Win over either those lol.
So "no" - since the only generation that pines in their beer over belts are boomers, they will almost certainly, slowly, die out.