SHA256 is an option. It's secure enough for Bitcoin.
That is why I think they’ll put more effort into exploiting badly written smart contracts than the underlying blockchain.
Ethereum projects get hacked every day, hackers make millions, but no one loses faith. More of a gravy train.
Really you need someone with a mission to crack bitcoin, not someone looking just to make money.
depends on what you mean by crack.
Although it is definitely better than SHA1, the improvement is ever so slightly:
SHA1 : ec1623b7a94ed3d8feaffaf7580df3eca4f5f5ca
SHA256 : e2b0c44298fc0c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855