it is different to know what the future holds
也许句子应该是：
It is difficult to know what the future holds.
想知道未来动向是困难的.
it是用来引导to know what the future holds的,原句相当于：
To know what the future holds is difficult.
整个动词不定式短语To know what the future holds（想知道未来动向）在句子中 作主语,is是系动词,difficult是表语.
different 是“不同”的意思,而difficult是“困难”的意思,看来这里用difficult较合理.