But only some elements were implemented into the btc system, so actually I'm not sure it is possible to make such a contract with it. At least it should be hard.
Nevertheless, we can't say that smart contract is a privilege of ETH since it's easy to build it with Byteball as well.
As for Ethereum surpassing bitcoin... I think it is rather likely to become as popular and as expensive as bitcoin is right now but not overcome it. ETH has its own issues due to many new opportunities it gives us.