I don't claim to know the future, but over the next 50 years [or 10 years or 500 years], I believe that the Christian church will move away from building-centered, program-driven megachurches, and newly manifest itself in smaller, incarnational groups or networks of groups. This will allow each church to have greater flexibility and adaptation for relevance and influence in each specific context in a rapidly-changing culture. It is even possible that American megachurches will one day stand as empty tourist attractions, like the vast cathedrals of Europe. Depending on what you read, this trend is already taking place now.
The question that further interests me is this: In this new manifestation, what will the role of the arts be? How will worship and devotional arts have impact in smaller settings? How will Christian art impact culture as it breaks through the confines of the building-centered worship service? In what new ways might art impact the world around us?