The reason for the decline is that there isn't much of a demand for a short range thumper like the Federal. If there were the .358 Win would be immensely more popular on the commercial rifle market as well. Believe me the .338 Federal is here to stay and the reloaders and rifle loonies will keep it going.
So, the Amercan hunter would not be best suited with short light rifle in a caliber that will take deer/antelope/elk at 0-300 yards?
The 338 Fed shoots the same bullet weights 50-100 fps faster than a 308 and 50-100 fps slower than 30-06.