Without a doubt, Bitcoin acts as a leading indicator for other cryptocoins, and many other asset classes globally by being a good proxy for the risk appetite.
With that in mind, given the historical ratio of Bitcoin/Ethereum, ETH has at least 2-3x upside now..;
Specifically, at historical highs ETH traded at ~10x the price of BTC/ETC, while now that ratio is ~30.
I.e. the honest pseudo-analytical statement is:
If everyone pulls the valuation for BTC out of a thin air, then the valuation of Ethereum should be pulled from much thinner air (i.e. higher clouds).