That PS+ version of Driveclub is not going to be the full game. It'll be a glorified demo.
Evolution has said it's the full game minus some tracks and cars, and that you will be able to upgrade to the full game at a discounted price. I guess we'll know more when they announce more.
Last I heard it would be free for PS+ but it would be a gimped version and even they full version was being delayed from launch day to 'launch window'.
Evolution confirmed on Twitter that it is still a launch title.