Ethereum popularity is due to the ERC20 tokens so everyone can create their own tokens using various ICO projects.
But the popularity is beginning to fade when there is a new generation of blockchain like Cardano and EOS and both coins both have the chance to become the next popular coin although it can not beat the dominance of bitcoin.
i think that nobody know the answer to you question because how would we know , and i guess that if they knew , they would not tell because they are going to be rich , but if i had to say 1 i would say NEO