Are you just looking at coins, which wants to be a real currency or are you also looking at tokens and platforms, where tokens could have differen use cases?
It is a really tough question anyways :)
Publicly mainstream could become something which doesn't look like a cryptocurrency or blockchain application/platform in the first place.
Also what is mainstream? Is it also mainstream when we see huge adoption at the B2B side or are talking about the B2C side ?
B2B could be VeChain, WTC, IOTA, NEO
B2C could be something like platform for digital items (esports) or a game-a-like blockchain.