Why would an omniscient God change his mind? That implies that He is capable of error. It implies imperfection in His decision making. When the Bible says God changes his mind, it is an anthropomorphism. God does not actually change His mind.
Yes, God knows what will happen. But that is not predestination. Predestination is about God setting a future event in stone. That is more than simply knowing. The Bible does not say that God chooses some to be saved. There is no such thing in the Bible anywhere.