I still believe that IOTA will eventually move up to number 3 in market cap at some point within the next year.
NEO may correspond with this question, not only by the future volume of the market, but also by the possibilities imposed for this currency.
but NEO is not the only one that maybe can replace Ethereum in popularidade, like this: Waves, EOS, Qtum, Stratis, may match the demand, though i believe nothing will beat Ethereum.