Who believes bitcoin dominance will fall to 20% in 2018?
bitcoin dominance will not fall below 99% for many many years.
the market cap percentage out of total however will be at 20% and much lower pretty soon.
With the strong rise of Ripple Ethereum Cardano Iota and more will it change the playing field?
all of them shitcoins with a huge premine and lots of coins unaccounted for but technically in circulation inflating their market cap
and if you believe it which currency could take over the #1 from bitcoin?
none of the altcoins.
unless you mean in market cap then Ripple is already #1 since it has 100 billion coins