Ethereum's price has mostly been fueled by the sheer value of all the ICOs conducted so far this year. The ether used to buy tokens in these sales are generally held back by developers in cold storage, effectively reducing the circulating supply.

The ethereum trade volumes have equalled that of bitcoins' in the past 2 days, probably because of the Bancor ICO which raised $150m (or 0.3 million plus ethers) . If trade volumes stay high even uptil next week then I am wrong. But bitcoin is much more liquid given the number of retailers who accept it and number of exchanges where it can be directly purchased for fiat. I don't think ethereum is as liquid yet. Bitcoin trade volumes should remain higher than ether for a while at least.

Given the last 2 years success, I think it is inevitable that Ethereum will overtake Bitcoin ("the filppening"). But the demand for ethereum will demand on whether ICOs manage to raise as much in the future as well.