The idea that God's predestination of some to believe is based on foreknowledge of their faith encounters still another problems: upon reflection, this system turns out to give no real freedom to man either. For if God can look into the future and see that person A will come to faith in Christ, and that person B will not come to faith in Christ, then those facts are already fixed, they are already determined. If we assume that God's knowledge of the future is true (which it must be), then it is absolutely certain that person A will believe and person B will not. There is no way that their lives could turn out any differently than this.
I have contended for some time that God's knowledge of future events does not remove free will, God simply knows what the person will freely choose to do in the future. In the past the same argument as Grudem's has been made here by open theists about God knowing future choices.