The problem is that historically changing the stdlib in a significant way rarely happens once a language has moved out of the lab, do to the sheer amount of breakage that would ensue.
That is not a worry for Rust. At this stage we make breaking changes to the standard library nearly every day. Sometimes on an hourly basis.
Revamping I/O is very high on the list. Brian Anderson et al are working on it as we speak.
However, I hate semi colons so I agree with you there. You should check out the nimrod programming language.