What would it take?
The world would have to be operating under a neo-fascist speech suppression economy. New coins would be banned, perhaps by only allowing internet traffic over ports 80, 443, and 8333.
The world is going to operate under a basket of currencies, where switching between currencies will be done with one tool, for free or less than .015%
Some currencies, although dinosaurs, will remain entrenched, for the same reason why people use Hotmail.com. Some currencies, will soar like eagles, living on the bleeding edge and pulling the intelligent market share.
PS, toldja OP is a Bitcoin maximalist. OP, I know you are frightened by these new-fangled coins. But I know that deep down in your soul you can see how the Bitcoin community has been divided, and as a result has become stagnant. Sometimes new coins are absolutely necessary. Case in point: one of the major reasons why Bitcoin's dev team sucks is the public knowledge of all core Devs. What if somebody went out and threatened their families with murder unless an exploit were to be inserted backdoor-style? Semi-anonymous Dev teams are superior