I shoot and hunt with nothing but factory ammo. I order almost 100% of all my ammo on line from places like Midway, cheaper than dirt, or Superior Ammo. The fact that I'm not a reloader has never influenced me in caliber choice.
Both my wife and I hunt with the .260 rem, and never had any problems finding ammo. It's honestly the last thing I worry about. The fact that every corner store, or ma and pop gun shop might not have .260 Rem ammo on their shelves never bothered me when I bought the .260. I can't walk into any Wally World, Dicks Sporting Goods, etc, around here and buy ammo for the 7x57, .257 Roberts, 7-08, 250 savage either.

I think the lack of entry level, mid priced rifle offerings in the .260 is hurting it far more than any ammo availability.