I tend to take a very long-term view. Long term, I can't see the .300 WSM and the .300 WM both surviving. They are too similar. Like everything else in business, there will be consolidation. One of the other will cease having rifles chambered for it and ammo will become scarcer, eventually becoming a hand loading only proposition.
My bet would be on the WM winning. Both have advantages (velocity vs. short action) but I think the WSM won't overcome the big head start of the WM.
The .300 H&H and .300 Wby will survive as cult cartridges with a small group of loonies.
As for the other .300 magnums recently introduced, fuggedaboudit.
