There is no saying what may happen.

很难说会发生什么事。

There is no saying what may happen.

说出他要干什么是不可能的。

There is no saying when he'll come.

很难说他何时回来。

There is no saying when he'll come.

很难说他什么时候回来。

There is no saying when he'll come.

很难说她何时回来。