Let's get something clear. When you say "cryptocurrency" you are talking about altcoins and even tokens. So the answer is no, altcoins are not even designed to be used for payment. Majority of them are completely useless and only have one purpose which is to get pumped and dumped.

That only leaves bitcoin and bitcoin is already used for "mainstream payments" in a lot of sectors. Even big companies like Microsoft have been accepting bitcoin payments.
However, I don't see the scale of it increasing anytime soon because the price is still on the rise and that makes people more willing to hold their bitcoins rather than spend them.