I keep hearing that the .308 and .30-06 are obsolete. I work at an outdoor retailer. A large part of our ammunition shelf space is .308, .30-06, and 6.5 CM.
I do not think we are in fear of losing the .308 anytime soon.
It is not a barrel burner so rifles will not "wear out". Average hunter maybe fires 5 rounds a year if they even do hit the range to check their zero.
The average hunter is not going to some custom rifle with a custom chamber that they need to hand load for.
I see hunters all the time shopping for the same ammo they have been using for years. They either get mad when the familiar green box is not on the shelf or they are content with just grabbing another brand with the same weight. "A 150 grain from these guys is the same as a 150 grain from these other guys right? No need to hit the range. It will shoot the same." No changing their mind when you suggest they go shoot it to confirm.
Might be the same with 6.5 CM in a dozen years or so.