Will Jesus' prayer for unity be fulliled? What would that unity look like? Think about it...

John 17:21,23
   That they all may be one; as thou, Father, art in me, and I in thee, that they also may be one in us: that the world may believe that thou hast sent me.
   I in them, and thou in me, that they may be made perfect in one; and that the world may know that thou hast sent me, and hast loved them, as thou hast loved me.

"That the world may believe"

"Some explain the word world to mean the elect, who, at that time, were still dispersed; but since the word world, throughout the whole of this chapter, denotes the reprobate, I am more inclined to adopt a different opinion. It happens that, immediately afterwards, he draws a distinction between all his people and the same world which he now mentions. The verb, to believe, has been inaccurately used by the Evangelist for the verb, to know; that is, when unbelievers, convinced by their own experienc, perceive the heavenly and Divine glory of Christ. The consequence is, that, believing, they do not believe, because this conviction does not penetrate into the inward feeling of the heart. And it is a just vengeance of God, that the splendor of Divine glory dazzles the eyes of the reprobate because they do not deserve to have a clear and pure view of it."

    –– John Calvin