In fifty years, the worship practices of the church will be all over the map--just like today! The good news is that people will still be assembling together for worship. The "virtual church" is an interesting idea, but it will not take the place of believers coming together in one place to do "the work of the people"--worshipping God. The good news is that those who plan worship will be comfortable drawing on all the many facets of the Christian tradition to do worship.
Music is always the big issue when we talk about worship. I think we will see less "contemporary" music and more music that draws on scripture (such as the Taize tradition), chants, classical music, and traditional hymns. This goes along with a general trend among young adults today to embrace mystery and transcendence in worship.
This also means more art, more candles, and--generally-a more experiential and participative approach to worship. The Eucharist--communion, Lord's supper--will be even more crucial to worship than it is today in many of our (Baptist) churches. In fact, many churches will observe the ordinance weekly.
What about preaching? Yes, the proclamation of the Word will still be vital to worship. Although in some cases it will be supplemented by visuals, I believe that the current resurgence in the oral tradition--especially story-telling--will continue. Media may enhance the presentation of the Word, but effective preaching and teaching will still rest upon the spoken word with clear explanation and appropriate application. We will probably even use more scripture in worship than we tend to do today--reading the text, listening to others read the text, and meditating on the text.
I think we will also see more opportunity for worshippers to share their own stories and to be involved in a dialogue with the preacher/teacher. This goes along with the participative nature of worship.
Worship will continue to be the "front door" of the church for most people, but many will come just to observe and learn about the Christian faith as expressed in worship.