Then if it is too late to buy ETH, my question can seem naive but I have to ask:
Which coins have that potential of a x000% increase in 2017-2017 ?
Nobody can tell such a thing. And I guess that if you want to invest in coins and sell everything till the end of 2017, ethereum might not be a good one. The price is already too big, I think it is ought to fall and then go up slowly. I think people omit it, but litecoin is a good coin to invest your money in. And it is still a cheap one. If you want to invest in eth, try to wait and see if the price is getting down.