I honestly don't see any cryptocurrency being used as a currency possibly ever but at least not until it stabilizes in value. You have to look no further than the real world to see what happens with unstable currencies. In countries like Venezuela for example a secondary economy forms around something stable like the US dollar.
The big problem with cryptocurrency is one of the things that many advocates claim as an advantage: there's no central bank who can affect the money supply. As much as people might, say, criticize the Fed for QE policies and central banks in general for "printing money", these things are actually necessary.
Bitcoin (et al) are like "digital gold". Gold as a currency had its place but there are huge problems with it and good reasons why the world went the way of fiat currencies.
So I see these coins being used ephemerally. For example: seller converts USD to BTC, spends that BTC on something. The seller immediately converts it back to USD so neither party has a holding period of BTC as there's too much risk attached.
That's all fine and there are definitely use cases for that. Unfortunately many of them are illegal so even though the tech is agnostic to such things, illegal uses are and will continue to be a big driver in cryptocurrency usage. This too will hurt widespread adoption.
As for the stellar rise in Bitcoin, I do think it will settle at some point for this reason: there has been a proliferation of other coins. At some point people are going to realize that these are interchangeable so you can just use whichever one you need to (again, ephemerally). New coins will fill the demand and they'll simply become another commodity.
Maybe that's the solution to the central bank problem.
Still, I can't help but wish I'd bought some Bitcoin at some point.