Folks love to talk about how all sorts of cartridges are "dead" for any number of reasons, some more valid than others, but in reality, no cartridge is really dead unless it has gone completely out of production, and even then there's always a possibility that it will someday see a resurgence in popularity.
There are some extremely obscure cartridges which remain in limited production to this very day, such as "9x18 Ultra" which was never a successful or popular cartridge to begin with, nor were many guns chambered in it.
So it seems rather absurd for folks to boldly proclaim that a cartridge as resent as .30 Super Carry is dead and that ammo production for the cartridge will cease altogether in a world in which 9x18 Ultra is still produced in limited quantities despite the fact that nobody has manufactured a firearm chambered in it since 1979 when the Walther PP Super went out of production.
My advice on the subject would be; if .30 Super carry seems interesting to you, then might as well buy a firearm chambered in it. That way even if it does go out of production in a few years, the firearm itself may become a valuable collector's item in years to come, and you'll get the last laugh over the naysayers because while they got to be right about something, you're the one who actually profited.
Besides, you never know... .30 Super Carry might gain a cult following in years to come, eventually becoming a cartridge shrouded in urban legends, and join the likes of other formerly "dead" cartridges such as 10mm Auto, 5.7x28, and .327 Magnum.
Personally, I'm anticipating an eventual resurgence in popularity for .357 SIG, as it has been getting lots of attention from certain ammo testers on YouTube who have been impressed by its performance, and seeing as .40cal pistols can easily be converted to the cartridge with drop-in barrels, it seems likely to maintain a strong cult following which will eventually prompt a comeback once enough influential individuals rediscover it.
