In answer to your original question, I would say the fulfillment of spirit potential takes the form of incarnation, transfiguration, resurrection and ascension. This transformation takes place "in Christ" and could be said to make the individual part of a larger unity, the resurrected body of Christ. In Christian theology, there have been many discussions of eschatology. Some of them place an emphasis on some dramatic future End Times. Other emphasize the here and now and the importance of Divine Immanence. Although some of Paul's descriptions do suggest a future that is not yet here, there are other parts of his gospel that emphasize existential immediacy and our ability to respond to G-d's Immanence.