Honestly Greg I see one of the great obstacles for Cryptocurrencies gaining Global Reserve standard is that they are very network and technology specific. There are still massive areas of the world, with a large population base, where people subsist on very little and a smart phone or internet access isn't an overly common item (rural India, much of Africa, ect.). Also, though there is an industry front runner (Bitcoin), with what little I know I could see there being constant new competition pushing the industry leader with feature advancements that early entrants wouldn't possess. I don't know how easy it would be for established Cryptocurrencies to alter their offering and keep up with functionality/security enhancements. I'm sure there are some knowledgeable people here who might be able to expand on this. :)