Yes, it would seem that the three witches have some limited knowledge of what is going to happen in the future, which implies that everything is foreordained. It is questionable whether Shakespeare really believed this or whether he only used it for his plot purposes in the one play of Macbeth. Philosophers have pondered and debated this question for centuries: do we have free will  or is everything predetermined by fate? Macbeth seems to be trying to assert his free will against fate in many parts of the play. He thinks he can prevent Banquo's descendants from becoming kings of Scotland by having Banquo and his son Fleance murdered, but Fleance gets away, and Banquo's ghost appears at the banquet to show Macbeth that the witches' prophecy is still going to be fulfilled. Macbeth believes he is invincible unless Birnam Wood moves to Dunsinane and/or he is overcome by a man who was not born of a woman. But both these things happen. Whatever is going to happen will happen. It is a very interesting question, and one that must have intrigued Shakespeare. In his  Julius Caesar  for example, he has Brutus say:

O that a man might know

The end of this day's business ere it come!

But it sufficeth that the day will end,

And then the end is known.