Like a centralized bank?
If you want a free market you need to accept that there will be price volatility. And people have been pouring in for the last year (as the chance to make money has become more present in the press).
To the OP, I believe Litecoin has the best chance of serving as a real currency of those you mentioned.
But keep in mind, it's not the consumers choice, it's the merchants choice. If they were to accept a cryptocurrency for payment, the consumers will flock to it and use it. You should shift your question - when will merchants decide crypto currency is something they want to participate in?