Crypto currencies have a promising future. However, I will say that the Altcoins that exist in the present will not be used as payments. The decentralization of cryptocurrency is a great advantage over the work of existing banks, but the governments of large countries are able to restrain the development of cryptocurrency.
I think some altcoins will be used as means of payment: ETH, Ripple for example. Especially Ripple, because it kind of stands apart from other altcoins.