Whether one of these systems gets widespread enough such that you can go out and buy your coffee or pizza using it - that remains to be seen. I am going to make a prediction that this is going to be more of a legal and economic battle than a technical one. The question is whether governments would be fine with having a cryptocurrency competing with their fiat currency, or whether they will just try to outlaw it. That will be an interesting thing to watch in the coming years.
One thing I am fairly sure of is that bitcoin is not going to be that currency, since it simply does not scale well enough. You can only do about 7 transactions per second, and on the bitcoin network you have to wait for an hour for the transaction to go through. Those things make it infeasible to be used as an everyday currency.
There are some proposals that are pretty close to performing as well as PayPal, but they still haven’t reached the sort of maturity that PayPal and other centralised systems have reached. So there is some technical progress yet to be made; someone needs to come up with a system that is comparable to bitcoin in terms of popularity, which can still be feasible enough to be used as a currency. But once that technical battle is over, which I don’t think should take very long, there is going to be a legal battle across the world.
I’ll put my money on 10 years until the time there is a feasible cryptocurrency, a globally feasible alternative to fiat currencies. The legal battle will start before then, because governments should see this coming.