The 358W has about reached the end of it's life
At one time there was some truth to this statement. Not long ago nobody was making rifles and there was only one factory load, the seasonal Winchester 200 grain RN.
In the last few years however, the cartridge has had something of a renaissance. There are 358 rifles regularly available from Browning and Ruger makes some from time to time. In addition to the venerable Winchester load, Hornady
has a new load as well.
So I don't see it replacing the 308 in popularity anytime soon, but it's far from dead.