Hard to sell modern America on a rifle that costs just about as much as a full-size rifle to produce, but yields 1/2 to 1/3 the oomph for the effort.
Yes, there are definitely many applications (actually most, I would argue) where a lighter-weight, lower power firearm would actually be advantageous over even something as mild as a 223, but you will never, ever, ever be able to market 'less' over 'more' as a product solution. Which is why the instant something larger came along to bridge the gap between pistols and 12lb battle rifles, 30 Carbine was left in the dust.
I do think we are at a unique period where a renewed focus on home/personal defense vs hunting, and increased participation by female shooters, will put emphasis on PDW type firearms, where something like the Carbine as a weapon format could come back into favor. If only because the closed-bolt PCCs they would compete with cost nearly as much but are even weaker. The only reason PCCs have taken off is due to ammo costs falling, so a PDW cartridge that could be similarly cheap & available would likely do quite well (like a 223 cut down to approximate 30 carbine with more available brass, for example, or a 45/308 case loaded to 38 Super length). Rather than straight-wall designs like the Carbine, I expect necked high velocity versions to dominate, to make best use of fragmentary bullets that are more effective for their bore size than simple expansion.
Personally, I think the only way the Carbine could see a resurgence is if we find & import a ton of new rifles & cheap ammo, or if 22 Spitfire finally sees popularity as a defense round.
TCB
!!!(!!!)