Ethereum is not a threat to Bitcoin. With time smart contracts will get bigger and more complicated. Complicated contracts can cause errors that can lead to ETH losses. So BTC will be more safe in a way because it's just a currency without any gimmick attachments.
Yes ethereum is not a threat to bitcoin as they have different perspective. Bitcoin is the strongest cryptocurrency and most used and supporters in bitcoin. Though ethereum has its own with smart contracts that most use in ICO project. So best use is the bitcoin and ethereum will not bypass the bitcoin.