I think to be the number 1 cryptocurrency in the future, Ethereum should have a fixed price in fiat money (~$1000), in order to become a reliable and non-volatile active for the holders.
Yeah, low volatility is one of the main features every coin has to posses to be acceptable as a currency. As to ETH value of ~$1000 it is arguable. In my view the nessesary requirement for #1 coin is as simple as following. Its cap should cover all remaining crypto.