in future相当于in time yet to come,意为“将来”,指较长的将来一段时间.
Who knows what will happen in future?谁知道将来会发生什么事?
I'd like to be a teacher in future.将来我想当一名教师.
for the future表示“为将来”,在句中作定语或状语.
We'd better lay up some money for the future.我们最好为将来攒一些钱.
It's necessary to plan for the future.对未来进行规划是有必要的.