It has been suggested that much of Luke-Acts (especially Acts) is written with the theological perspective that the early church now has seen Jesus go away and is trying to cope with how this is a supposed *victory* over the world. In other words, the church must now figure out how the resurrection is meaningful, and how we are going to make it through until the return of Christ back to his people - in which case he will then establish his reign and rule over the world. This has serious ramifications for our understanding of the text, its historical circumstance, the development of Christian theology, and the manner in which churches are built up in the present.
But this reading, though often prevalent, does serious injustice to what Luke is trying to say in the text. Luke does not give us an *absentee christology* like so many would like to assert. This completely misses the portrait which is given through the Gospel, that Jesus' ministry is concerned with the full restoration of Israel and that his resurrection is the definitive act in establishing his vindication to reign over creation. His ascension in Acts 1 is not the removal of Christ from the church, but his enthronement over the powers which work against God in the world. And thus he is able to send his Spirit to every believer - building up the church, comforting and guiding in the work of the kingdom, and making his presence available to all creation.
Thus, through the church - the entity which is given as the working of Christ's kingdom in the world - he is establishing his dominion of life and light into death and darkness. So, it is not as though Luke is scrambling around to construct a theology which will keep his community optimistic about the future. Instead, he writes a narrative full of discovery that the true reign of God, the fulfillment of the hopes of Israel, have come into the present world (on this, see many works by N.T. "Bishop of Awesome" Wright). The conflict which comes demonstrates the fulfillment of Israel's covenant (Jervell), but also the battles which serve to define an 'in-between' period before the ultimate realization of the kingdom.
If Jesus is then God's Messiah - the one who has been exalted to share in the power and dominion of Yhwh - then the storyline of Acts is built upon the realization of Israel's restoration has broken into the world. Acts 3:21 serves to highlight this regarding Jesus: ". . .who must remain in heaven until the time of universal restoration that God announced long ago through his holy prophets." The fundamental idea of holiness which moves outward from the point of interaction with Yhwh (once the Temple; now the Spirit) continues onward in new profundity along Luke's narrative.