Crown Princess Victorias wedding will most likely take place in Storkyrkan (Stockholm Cathedral) but a few other churches in Stockholm can also host a big royal wedding.
They are Engebrektskyrkan at Östermalm, Gustaf Vasa Kyrka at Odenplan,
Högalidskyrkan at Södermalm and St Johannes Kyrka in the central of Stockholm.
Off course the Palace Church can also host a royal wedding but not with more than 700 guests and I guess it will be more at Victorias wedding.
The royal palace church will most likely be used for the christening of Victorias, Carl Philips and Madeleines children and also for the funeral of members of the royal family except for The Moarch and his / her consort and the heir apparent if he /she die before the accesion. Their funeral will take place in either Storkyrkan or Riddarholmskyrkan.
Another possible church for the christening of Carl Philips and Madeleines children is Räpplinge Kyrka at Öland, frequently used by the royal family in the summers when they are at Solliden Palace.
But I think we can say that the wedding of our Crown Princess will take place in Storkyrkan.