Never. We need to understand that while Bitcoin is a currency, a means of payment, Ethereum is a platform for launching Decentralized applications.

Nature: Consider comparing Bitcoin to Gold and Ethereum to Iron Ore. Gold is a store of value and Iron Ore is the building blocks of so many things we use in daily life.
Supply: Bitcoin is deflationary whereas Ether is inflationary. There will only be 16mil BTC. The current supply of Ether is close 97mil. Using the basic principal of Demand and Supply, a commodity that is scarce will have more value - Bitcoin.
While one is a store of value/currency, the other can be looked at like a stock.

So, no, Ethereum can not overtake Bitcoin in terms of price.