Ethereum is a great indicator for the bullrun of Altcoins - "Alt Season". The red circle to the left points at the beginning of the last Alt Season in 2017.
Ethereum is heading to an attractive price level pretty soon where more and more people will be likely to pick it up. Most Alts are at the same stage of their market cycles or even further down. Since Ethereums reputation is not the best currently it might have to go even further down to find a valuable price for most investors.
I expect the first Alt Season of 2018 to start around April/May 2018.