According to an article in the Associated Press, the new opera house, which was built on behalf of and donated to the city of Copenhagen by Mærsk Mc-Kinney Møller (through his foundation), will open on 15 January 2005. Noted is that the ballet will use the opera house when the repertoire requires a large orchestra.
On another thread -- I apologize, Effy, for starting a new one -- Effy notes that the opening will be televised, and lists the ballet performances that will be part of the opening gala (click here).