There are a lot more dead cartridges than people realize because essentially they've stopped producing much if not all of many of the common cartridges that used to be available at your local Walmart or hardware store.
This ^ and if you factor in component availability as well you can see some real declines or non starters.
30-06 will have a long life due to the amount of brass on the planet.
Maybe the question should be "What cartridges have the shortest life?" 7mm RSAUM?
It would still be popular with the F-class crowd if brass was widely available.
One expensive supplier not named Lapua isn't enough.
or 30 Super Carry? Yes it is new but there are only a few manufacturers for the pistols,
though Hipoint does make a carbine for the 30 SC. No one sells brass yet though.
Never good for a cartridge when you can't find brass.
Maybe it will take off. Would love to see some of the pocket 32s switch to 30SC.
There can be some the benefit to newer cartridges.
For instance, higher SAAMI chamber pressures resulting in better (usually) performance.
Don't have a 222 or a 6.5x55 ...yet

however they have a following and still get made to some extent.
I will admit that I did buy a Remington Etron-X in 22-250 along with a case of ammo.
Have since sold it when I couldn't find the primers any more. The electric primer never did take off.
Popularity certainly fluctuates unfortunately it is hard to get past lack of components.