The 8mm Rem Magnum was not killed by the name, but rather, as much as anything else, by the fact that no premium .323" (8mm) bullets were available. Now we have Nosler Partitions (200 gr.), Swift A-Frames (200 & 220 grains) and Barnes X bullets, (180, 200 & 220 grains). There are others such as Woodleigh and Hawk, as well.
Pesonally I don't see the .325 Win Short Mag as a sufficient impreovement over the .300 WSM, but it does have a larger bore, heavier bullets and it will be superior on larger mammals such as elk and moose. The availablility of decent bullets will contribute materially to this cartridge's success, if it is to enjoy success.