Predestination has to do with the foreknowledge of God. Before God predestines anyone, He must first know them as a son. Now that God has foreknowledge of one as a son, God predestines them for the future adoption of sons. That's the destination of the believer, the redemption of the body.
29 For whom he did foreknow, he also did predestinate to be conformed to the image of his Son, that he might be the firstborn among many brethren.