In "Word Focus" Glenn McClure writes:
The other word is predestinate. This word conveys the idea of limiting in advance or marking out beforehand.
It should be noted that the verses where this word occurs relate to God’s redemptive plan for those who are “in Christ,” that is, believers. So we can see that predestination is primarily a doctrine for the saints, not for sinners.
Here we need to ask the right question. It is not who are the objects of this predestination, but to what they are predestinated. The text simply says that the believers are predestined “to be conformed to the image of his Son.”
It is only natural that the believer should be Christlike, for in Him is our total salvation dependent.
Source: Studies in Romans: Adult Teacher's Insights, page 46.